1. In the seeding year the total dry-matter yield in swards sown without a cover crop was increased by infrequent defoliation, but the yield of crude protein was decreased. The highest production of starch equivalent was obtained when a cover crop was used.

2. In the absence of a cover crop, the yield of red clover was higher under infrequent defoliation, but the yield of white clover was higher under frequent grazing.

3. Frequent grazing, and the use of a cover crop, reduced the ingress of weeds more than infrequent defoliation. Nitrogen applied to the cover crop also reduced the growth of weeds.

4. Nitro-chalk increased the total yield of herbage except when under a cover crop; it reduced the growth of red and white clovers, but this was not so marked under frequent grazing.

5. Nitro-chalk increased the annual yield of crude protein under frequent grazing, but decreased it in all herbage mixtures under infrequent defoliation; nitrogen had no effect when a cover crop was used. The increase in yield of starch equivalent due to the application of nitrogen and its apparent recovery was greater under frequent grazing than under the other two managements. Under infrequent defoliation, in the absence of a cover crop, the recovery of nitrogen was particularly low.

6. The ryegrass mixture and ryegrass-dominant general-purpose mixture made more growth, and suppressed clover and weeds to a greater extent than did the timothy and cocksfoot mixtures. This was modified by management in that ryegrass was particularly aggressive under frequent grazing (management 1) but not under managements 2 and 3.

7. In the autumn of the seeding year the yield of total herbage was highest under infrequent defoliation, particularly in the cocksfoot, and general-purpose swards. All undersown mixtures gave lower yields than when no cover crop was used.

8. Nitrogen increased the yield of herbage in May and June under frequent grazing, and in the August cut under infrequent defoliation, but in the autumn particularly it was reduced where a cover crop was used.

9. The application of nitrogen decreased the protein content in all herbage mixtures when a cover crop was used or when defoliation was infrequent. Under frequent grazing the nitrogen increased the percentage of crude protein in the first two grazings, but decreased it in the September grazing.

10. The production from the various mixtures was modified by management: under frequent grazing in May the ryegrass-dominant mixtures were higher yielding than the others, but in July the general-purpose and cocksfoot swards were the most productive. Under infrequent defoliation in August the timothy mixture had the highest yield and cocksfoot the lowest, and under this management cocksfoot and timothy swards had the highest yield in the autumn of the seeding year.

1. The method of establishment markedly affected the yield of red clover in the first harvest year, the highest yield being obtained when a cover crop was used, in the absence of which red clover yield was reduced by frequent grazing during establishment. White clover made little growth in the first harvest year; the yield was best without a cover crop under frequent grazing during establishment.

2. Nitrogen applied in the seed bed did not affect the growth of red clover in the first harvest year, but depressed the white clover under infrequent defoliation without a cover crop. There was no significant effect under the other management.

3. The total yield of red and white clovers was lower, when sown with the rapidly establishing ryegrass or ryegrass-dominant general-purpose mixtures, than with cocksfoot or timothy mixtures. Weed growth, although not prominent, was far greater in the timothy and cocksfoot swards than in those based on ryegrass.

4. A close parallel existed between the growth of red clover and the dry matter and yield of crude protein. The highest figures were recorded when management during establishment had favoured the growth of the red clover.

5. Nitrogen applied in the seed bed reduced the percentage of crude protein in all mixtures in the spring and autumn grazings, and in the hay crop of the first harvest year. Management which encouraged the growth of red clover increased the crude protein percentage of herbage in the spring and autumn, but depressed it in the aftermath cut.

6. A number of interactions occurred when the relative yields of dry matter and crude protein of mixtures in the first harvest year were modified by treatments applied during establishment. There are significant indications that the method of establishment is a factor to be considered in evaluating various mixtures.

The following conclusions were obtained from a comparison of growth and carcass characteristics of pigs slaughtered at 150, 200 and 260 lb. liveweight.

(a) The ranking of boars at the three weights, according to the quality of their progeny at each weight, was similar for the carcass characteristics, i.e. percentage of lean meat, length, backfat and eye muscle area—but was not associated for the efficiency factors, i.e. daily gain and food conversion. Results from singly-penned progeny pigs confirm that food consumed up to 150 lb. live weight is not indicative of the food consumed between 150 and 200 lb. live weight. A similar result is true for daily gain. It thus does not appear that the results obtained at 150 lb. live weight could be used to represent results at heavier weights and this is particularly true for performance testing when only one animal is concerned. Rather it would appear that if the pigs were raised to a given weight, carcass information at an earlier weight could be obtained on the live pig by ultrasonic means and by subjective estimates, whilst food conversion and daily gain could be calculated exactly at any live weight.

(b) The weights of the different cuts as a percentage of the side weight does not appear to change much between slaughter weights. The carcass becomes less lean as the slaughter weight increases and this difference in leanness is more observable between the 200 and 260 lb. weights than between the 150 and 200 lb. weights. In these ranges at least as much lean as fat is put on in the shoulder and ham but more fat than lean is put on in the back and in the streak. For example, between 200 and 260 lb., 5 lb. of lean to 9 lb. of fat is added in the back cut.

(c) For all cuts and for both sexes, the percentage of lean meat added in the range 200–260 lb. live weight is less than that for the range 150–200 lb. live weight. This difference is more severe for hogs, especially in the back cut. The sex difference (in favour of the leaner gilt) becomes more pronounced at the heavier weight range. This is not so obvious in the ham but is marked in the shoulder and streak and particularly in the back. 3·9 lb. of food is required to put on 1 lb. of live weight between 150 and 200 lb., whilst 4·3 lb. of food is needed for each 1 lb. gain between 200 and 260 lb. live weight.

(d) Percentage of lean meat prediction equations fitted to the data at the three weights are of equal accuracy. In all cases the reduction in variance is highly significant and the percentage of lean meat of a pig can be estimated with a standard error of approximately 2% of carcass weight.

Correlations between various characteristics at each weight indicate that (i) a good percentage of lean is associated with increased bone, a larger eyemuscle area and, in particular, less backfat; (ii) the carcass conformation score for 260 lb. hogs has a high negative association with average backfat and this may be because the extreme amounts of fat on some these hogs adversely affected the balance of the carcass.

Visual scores or assessments made on the shoulder, ham, streak and on the carcass conformation bear no relationship to the proportionate weights or to the leanness of the respective parts of the carcass. They reflect only the requirements of the trade which are based on shape and are not substantiated by dissection. In nearly all cases, gilts achieve better scores than hogs. The back rasher score assessed on a good fat to lean ratio and a good eye muscle is much higher for gilts than for hogs and decreases as the slaughter weight increases. There is a positive association between back rasher score and the leanness of the back.

Four hundred and twenty-two ewes, of a number of different breeds and ages (flocks 1–9) were used in experiments with hormones in the normal breeding season. Two main trials were conducted, the first making use of 377 animals, the second involving 45.

Trial 1

Three hundred and seventy-seven ewes were observed, in eight farm flocks, in a study of response to different treatments involving the administration of progesterone (in oil solution) and p.m.s. The trial sought to determine the effect of various dosage levels of progesterone and intervals of injection on the normal breeding performance of the ewe. Hormone treatment was applied at such time in the breeding season as to make it most improbable that conception would be limited by adverse animal or environmental factors. The aim was to determine the effect of the hormone technique per se on both immediate and long-term reproductive performance. Injection procedures and methods of flock management were arranged so that they might later be repeated in applications during the period of anoestrus.

Two hundred and thirty-three ewes were injected intramuscularly with doses of progesterone in oil solution over a 7-day period. For eighty-nine ewes, four doses of 40 mg. were administered at 2-day intervals; for 144, 3 doses of 50 mg. were given at 3-day intervals. A single injection of 750 i.u. of p.m.s. was given subcutaneously to each ewe 2 days after the final dose of progesterone. One hundred and forty-four ewes remained untreated and served as a control.

Progesterone therapy was effective in inhibiting oestrus and ovulation in the majority of ewes. Most injected animals came in oestrus 1–5 days following the injection of p.m.s.; 10% showed evidence of ‘silent heat’. 70% of ewes receiving progesterone at 2-day intervals and 68·2% of those receiving it at 3-day intervals conceived at the ‘controlled’ oestrus. 75% of the controls conceived at first mating. Treatment did not adversely affect the conception percentage to any appreciable extent.

In animals conceiving at first oestrus, the average number of lambs born per ewe was 1·78 for injected and 1·44 for controls. In each flock there was an increase in lamb-crop, which would seem to be the result of the p.m.s. injection. Information on the effect of therapy on subsequent ewe fertility shows that 6·4% of ewes failed to conceive; this figure was the same for both treated and control animals. An attempt to use A.I. in conjunction with progesterone- p.m.s. therapy gave a conception percentage of 24, as compared with 68 in normally bred sheep.

The results are discussed in relation to factors such as breed and age of ewe, and according to the particular mating procedure employed. There is no evidence that the forms of progesterone-p.m.s. therapy employed in this work would constitute a limiting factor to conception in out-of-season breeding.

Trial 2

The forty-five mature Welsh Mountain ewes used were in one flock. Each animal was injected on the 13th day of the oestrous cycle with a single dose of either 50 or 100 mg. of a micro-crystal suspension of progesterone. Two forms of suspension were used, the difference between the two being in the size of the individual crystals. Ewes came in oestrus 7–13 days following injection, the range for 50 mg. dosage being 7–13, and for 100 mg. 10–13 days. 25% of animals showed ‘silent heat’. Results suggest that injection of suspension adversely affects the normal expression of oestrus.

This paper deals with the application of various forms of progesterone-p.m.s. therapy to lactating and non-lactating ewes in the anoestrus of 1957. Twenty-one farm flocks, and a total of 753 sheep were used in three trials (3–5). In trials 3 and 4, the treatment employed techniques similar or identical to those employed in the previous breeding season (Part I of this series). Trial 5 was concerned with the use of micro-crystal suspensions of progesterone as a possible means of simplifying hormone administration procedure; again this was a follow-on to work in the 1956 breeding season. Applications of progesterone-p.m.s. therapy were made at two periods in anoestrus, April to May (deep anoestrus) and June to early August (late anoestrus). Observations on the occurrence of spontaneous breeding were made following hormone applications at these two periods, and studies on ram libido and fertility attempted. The main objective of the work was to determine whether low conception percentage is due to defective ram performance or to a failure in the supply of hormones essential for the maintenance of pregnancy. A preliminary attempt was made to induce previously injected ewes (lactating and non-lactating) to show a ‘repeat’ oestrus by extended treatments with progesterone and p.m.s.

Trial 3

Three hundred and twenty-one ewes, predominantly Chin Forests, were treated in April/May in twelve flocks. In five of these some proportion or all animals were lactating at time of injection. Six different combinations of progesterone and p.m.s. were employed. The majority allowed for pretreatment with progesterone over a 7-day period; doses of progesterone varied from 25 mg. (at daily intervals) to 50 mg. (at 3-day intervals). In each ewe, a dose of 750 i.u. freeze-dried p.m.s. was given 2 days after the final progesterone dose. One hundred and eighty-eight ewes mated (58·6%) 1–5 days after the end of treatment. The oestrous response was affected by various factors of treatment and animal. Progesterone treatment over 7 days gave rise to a higher response than did treatment applied over 5 days. Evidence of low libido in some rams was obtained, and possible methods for overcoming this problem are described.

Sixty-six of the ewes conceived and produced lambs, this being 20·6% of all animals injected and 34·4% of ewes which mated. An average of 1·39 lambs born per ewe conceiving was recorded. Nonlactating ewes conceived more readily (41·5%) than lactating (17·4%). Where ewes were subjected to extended hormonal treatment, to induce a ‘repeat’ oestrus, 26·9% conceived at first induced oestrus and 54·1% at the ‘repeat’ oestrus, a difference which was statistically significant (P < 0·05).

Trial 4

Three hundred and thirty-two non-lactating ewes, differing in age and breed, were used in studies conducted mainly in June/July. Eight different combinations of progesterone and P.M.S. were employed. For the majority, progesterone was administered over a 7-day period at 2-day (40 mg.) or 3-day (50 mg.) intervals. A single dose of 750 i.u. freeze-dried p.m.s. was given 1–4 days after final progesterone injection. Two hundred and eightyfive animals (85%) were served 1–5 days after the end of treatment. Ninety-two ewes conceived at the induced oestrus and produced lambs; as a percentage of those injected this is 27·7, and as a percentage of those that mated, 32·6. Average number of lambs born per ewe was 1·72. In the ewes which ‘repeated’ spontaneously after hormone treatment, 58·9% conceived. This was a significant increase over conception percentage at induced oestrus, but the average number of lambs born per ewe was lower (1·25).

Results on oestrus, conception and lambing in trials 3 and 4 are discussed in relation to treatment, ram fertility, breed and age of ewe, and several environmental factors. They indicate strongly that conception failure lies at time of implantation of the egg, possibly due to some inadequacy in the uterine environment. Conception may be facilitated where animals are either hormonally induced to show a ‘repeat’ oestrus or show it spontaneously. Factors of fundamental and practical interest in out-ofseason breeding are described, including length of gestation, incidence of lamb mortality and pregnancy toxaemia.

Trial 5

A total of 100 ewes, of several breeds and ages, and including sixty that were lactating received treatment with a micro-crystal suspension of progesterone, either in conjunction with p.m.s. or with doses of progesterone in oil and p.m.s. Treatments were applied in five individual groups during the period of deep anoestrus (April/May). The majority of ewes were given an initial injection of 50–200 mg. suspension, followed 7–8 days later by a single dose of 25 mg. progesterone in oil solutions; 750 i.u. of p.m.s. was administered 2 days after the final progesterone dose. 13% of animals mated after treatment and 2% conceived and produced lambs. The results for oestrus and conception were considerably poorer than those following the normal progesterone-p.m.s. technique.

Following preliminary work conducted in Part II of this series, an attempt was made in the anoestrus of 1958 to provide further information on the conception percentage which follows hormonal induction of a ‘repeat’ oestrus. Two hundred and twenty-one ewes, seventy-six of which were lactating (lambs 8 weeks or older), were available in seven farm flocks. Ewes were of several different breeds and ages but excluded yearling or maiden animals. The trial was conducted during anoestrus over the period starting 26 April and ending 2 August. Treatment consisted of the repeated application of the following injection sequence: three doses of 50 nig. progesterone in oil solution, given at intervals of 3 days, with a dose of 750 i.u. p.m.s. administered 2 days after the final progesterone dose. This therapy was repeated after an interval of 7 days; a 15-day-period therefore separated the two administrations of p.m.s., i.e. approximating to one ovarian cycle.

Rams were joined at the cessation of therapy; in most flocks, one ram was allowed for every ten ewes injected. Two hundred and six of the ewes came in oestrus (93·2%) over the period 2–8 days after the final p.m.s. dose. The oestrous response varied little among flocks, the percentage in oestrus rangingfrom 85 to 100%. One hundred and forty-one conceived at the induced ‘repeat’ oestrus (63·8%) and produced a total of 207 lambs (1·47 per ewe). As a percentage of ewes mating, 68·4 conceived. In none of the flocks did the conception percentage fall below 50; lactating ewes conceived as readily as ‘dry’ sheep. The period during which autumn lambings occurred varied from 4 to 8 days among the flocks.

The results strongly suggest that a much higher conception percentage is likely to follow this extended treatment than follows normal progesterone-p.m.s. treatment. From the practical viewpoint, the technique has the disadvantage that eight injections are necessary and that treatment is prolonged to a 24-day period.

Four trials, involving 245 ewes, were undertaken in attempts to reduce the prolonged hormone injection procedure necessary in the application of repeated progesterone-p.m.s. therapy. A continuous-injection apparatus was used as a possible means of rendering progesterone administration simpler. Information was sought on the oestrous and conception response where the first injection of p.m.s. was not preceded by progesterone therapy. Previous studies having indicated that oestrogen-progesterone balance may be important in the development of a suitably receptive uterine environment, two trials were conducted in which oestrogen therapy was combined with progesterone-p.m.s. treatment.

Trial 7. The use of a continuous-injection apparatus was studied in sixty-nine ewes, of several breeds and ages, in four farm flocks. Apparatus were used to administer progesterone in propylene glycol solution over periods of 7–12 days. They were adjusted to give an average daily output of progesterone ranging from 5 to 15 mg., administration being made subeutaneously. In twenty-five the function of these over the planned period of administration was considered satisfactory. A subcutaneous injection of 750 i.u. of p.m.s. was given when the apparatus was removed. Twenty-five per cent of the ewes mated after the treatment; of these, only 25% conceived and produced lambs. The poor response would appear to indicate that low dosage level parenteral progesterone therapy may be much less effective in facilitating oestrus and the conditions necessary for conception than the administration of single doses of greater magnitude at daily or longer intervals.

Trial 8. Fifty-one Clun ewes, of mixed ages and non-lactating, were arranged in two comparable groups. One group (twenty-five ewes) received an injection of 750 i.u. p.m.s. prior to the commencement of progesterone-p.m.s. therapy; the remaining twenty-six animals received progesterone-p.m.s. only. Combined treatment consisted of three doses of 50 mg. progesterone at 3-day intervals, with 750 i.u. p.m.s. given 2 days after the final progesterone injection. In animals receiving two injections of p.m.s., the interval separating such treatments was 15 days. Of the twenty-five ewes receiving prior p.m.s. treatment, fifteen (60%) mated, as compared with 54% of those which did not receive prior treatment. For ewes receiving two doses of p.m.s., the conception percentage was thirty-three, as compared with forty-one in the controls. The results indicate that repeated progesterone-p.m.s. therapy may not be conveniently simplified by a treatment in which the first p.m.s. injection is not preceded, by progesterone.

Trial 9. Eighty-five Half-Bred maiden yearling ewes were arranged in two groups. In one, a single dose of 50 μg. oestradiol was administered 24 hr. prior to commencement of progesterone-p.m.s. therapy; the second group (control) received progesterone and p.m.s. only. In each group, 10 mg progesterone was injected daily for 12 days, and 750 i.u. of p.m.s. administered 24 hr. after cessation of such treatment. Sixty-one per cent of oestrogentreated ewes and 78% of controls mated. There was no significant effect on conception; 33% of those which mated after receiving oestrogen conceived as compared with 41% in controls.

Trial 10. Forty mature, lactating Clun ewes were observed after a treatment consisting of seven daily injections of 25 mg. progesterone, with a single dose of 750 i.u. p.m.s. given 2 days later. Thirty-six ewes mated, and eighteen were injected with a single dose of 50 μmg. oestradiol 3 days after service. Fifty per cent of the oestrogen-treated ewes and 11·1% of the controls conceived. Results suggest that oestrogen treatment following mating may facilitate conception by its action on the uterus.

This trial concerns the induction of pregnancy in two flocks of Clun maiden yearling ewes and involves seventy-six animals. Previous observations suggested that treatment of this particular category usually gives rise to a higher conception percentage than is found with dry post-partum or lactating sheep. The trial sought to elucidate some factors of animal and environment which may be associated with this response.

In flock 45, during the period 10 February to 29 March, observations were made on the incidence of spontaneous breeding activity in forty-seven ewes; hormonal therapy was first applied at the latter date. Treatment for all ewes consisted of three doses of 50 mg. progesterone (in oil) given at 3-day intervals; a single dose of 750 i.u. p.m.s. was administered 2 days after final progesterone.

Nineteen of the forty-seven ewes (40%) in flock 45 showed spontaneous oestrus in February or March. Three (16%) of those ewes previously mated came in oestrus after treatment; forty-nine of the fiftyseven unmated ewes (86%) showed oestrus 3–5 days after the end of injection. Of the nineteen sheep that mated spontaneously, ten (53%) produced autumn lambs. Twenty-six of the fifty-two sheep (50%) served in response to the progesterone-p.m.s. therapy conceived. 1·25 lambs were born per ewe that lambed. Some evidence for total embryonic or foetal loss in the ewes during pregnancy was obtained. Results indicate that conception in these maiden ewes may have been facilitated by the presence of corpora lutea or recent luteal activity, which maintained the oestrogen-progesterone balance necessary for providing an adequate uterine environment. For this reason, maiden ewes of breeds with short breeding seasons (e.g. Scotch Half-Breds) may not give such satisfactory response when injected at times comparable to long season breeds, such as the Clun.

Field trials on hexoestrol implantation were conducted in the Waikato area of the North Island of New Zealand during 1958–59, involving 260 two and three year old Aberdeen Angus steers from nine farms. Two levels of hormone implantation were studied, namely, 30 and 45 mg. The trials ranged in duration from three to five months with an average of four months.

Pronounced differences were apparent between farms in the overall growth rates and carcass quality scores of the cattle.

Hexoestrol implantation led to a significant increase in carcass weight, estimated at approximately 22 lb., with little evidence of real differences between farms in the average response to the hormone.

Response to the higher as compared with the lower dose of hexoestrol varied markedly among the separate farms. In general, the lower dose of 30 mg. tended to yield the greater increase in carcass weight.

A small, but consistent, depression of carcass quality scores was manifest under hormone treatment, with no real differences between the two dosage levels.

1. A balanced factorial experiment was carried out with 48 Merino ewes. There were two levels of each of the four factors: environmental temperature, thyroxine status, vitamin A intake and progesterone status. Each ewe was killed at 25 days' pregnancy. The thyroid was removed, weighed and examined histologically.

2. Thyroid weight in the hot-room animals was significantly decreased by large doses of vitamin A. It was not affected by any of the other treatments.

3. With respect to the number of follicles per unit area of cross-section, the following interactions were significant: temperature × vitamin A; temperature × progesterone; temperature × vitamin A × thyroxine. The directions of the effects of vitamin A and of progesterone were reversed by the higher temperature.

4. There were no significant effects on nuclear height in the follicular epithelium.

5. The frequency of marked ‘scalloping’ at the edge of the colloid was significantly higher among those ewes receiving thyroxine injections than in the remainder. This feature was not significantly affected by any other factor.

1. A balanced factorial experiment was carried out with 48 Merino ewes. There were two levels of each of the four factors: environmental temperature, thyroxine status, vitamin A intake and progesterone status. Each ewe was killed at 25 days' pregnancy. The ovaries were removed, weighed and examined histologically.

2. There were no significant treatment effects on ovarian weight, corpus luteum diameter, lutein cell frequency, lutein cell nuclear diameter, the number of Graafian follicles exceeding 0·9 or 1·9 mm. diameter, or mean follicle diameter. The results suggest that with more animals heat might prove to depress ovarian weight and vitamin A to increase ovarian weight, corpus luteum diameter and the number of large follicles.

3. There were no significant differences between the mean values for those ewes with live embryos and those with dead ones with respect to any of the above indices.

4. The results support the conclusion that variations in embryonic viability due to the experimental treatments were not mediated primarily through variations in ovarian hormone secretion.

1. A balanced factorial experiment was carried out with forty-eight Merino ewes. There were two levels of each of the four factors: environmental temperature, thyroxine status, vitamin A intake and progesterone status. Each ewe was killed at 25 days' pregnancy. The embryos and their membranes were weighed and examined histologically.

2. There appeared to be no treatment effects on the embryonic length/weight ratio. The ratio between embryonic weight and ‘conceptus minus fluid’ weight may have been affected. There was no evidence of treatment effects on the degree of differentiation of either the embryo or the chorioallantois.

3. Surviving embryos tended to be large where thyroxine was supplied, i.e. where viability was good, and vice versa. Dead embryos fell into two groups: those less than 3 mm. long and those 6 mm. or more which had probably died shortly before the ewes were killed.

4. There were no significant correlations between the weights of live embryos and mean rectal temperature, plasma vitamin A concentration or any of the histological indices measured in the endometrium. In the hot-room live embryo weight was correlated with the height of the ewe's bladder epithelium (P < 0·01).

5. It is suggested that in the absence of adequate maternal thyroid hormone (i) the trophoblast may enlarge too slowly to stimulate adequately some response in the endometrium essential for maintenance of the embryo, or (ii) disproportionate growth in different parts of the conceptus may result directly in embryonic failure.

1. Rectal temperatures and respiratory rates have been determined in four calves during 5 hr. exposures to ten different hot environments in a climatic room.

2. Among the various parameters based on rectal temperature response, final rectal temperature proved the best for differentiating between the heat tolerance of individual animals. Under conditions of severe heat, where rectal temperature rose almost linearly with time of exposure, tolerance time proved equally suitable.

3. Since initial rectal temperature tended to parallel final rectal temperature, the increase in rectal temperature during exposure did not vary significantly between the animals. Increase in rectal temperature was therefore considered a less suitable measure of heat tolerance.

4. Both the lowest and the highest panting rate were associated with a low heat tolerance. From this, as well as from other observations and considerations, it was concluded that respiratory rate, either alone or in combination with rectal temperature, was an inadequate measure of heat tolerance.

5. A state of high heat tolerance tended to be associated with only a small loss of body weight during exposure to heat, but showed no relation to body weight itself.

6. The order of heat tolerance of the four animals was essentially the same in each of the ten hot environments investigated. It was inferred that within the range of temperatures employed in this study the degree of severity of the heat stress was not an important factor in the discrimination of heat tolerance.

… In short, he used many learned arguments to persuade his audience out of their senses; and from stench made a transition to filth, which he affirmed was also a mistaken idea, in as much as objects so called, were no other than certain modifications of matter, consisting of the same principles that enter into the composition of all created essences, whatever they may be: that in the filthiest production of nature a philosopher considered nothing but the earth, water, salt and air of which it was compounded.…

1. When Merinos of varying wool lengths were exposed at constant air temperature of 36° C. (c. 97° F.) to infra-red radiation of energy equivalent to that which they might receive from the sun, the following responses were noted:

(a) A very highly significant (P < 0·001) inverse relationship between respiration rate and wool length.

(b) A non-significant inverse relationship between rectal temperature and wool length.

(c) A very highly significant (P < 0·001) quadratic relationship between back wool-tip temperature and wool length.

(d) A very highly significant (P < 0·001) inverse relationship between back-skin temperature and wool length.

Thus, the length of wool determines to a large extent the degree of protection given to the sheep against radiant heat.

2. The rate of conduction of heat per unit area through the back wool in different sheep was hyperbolically related to wool length. Below 1 cm. woollength heat was taken up very rapidly; beyond 4 cm., increasing wool length afforded negligible additional protection.