In 1914 the result of a study of the evaporation of water from soil was published by B. A. Keen, who distinguished two factors governing the rate of evaporation. One factor was that the available surface from which evaporation takes place decreases as the moisture content decreases. Keen deduced an equation that expressed the operation of this factor, viz.

in which D is a constant, w = percentage of water by weight and s = the real specific gravity of the soil. He showed that this equation agreed with his experimental results with a reasonable degree of accuracy.

1. Further confirmation is presented in support of the relationship between the presence of vitamin A in the milk and its supply in the food.

2. The influence of the supply of the vitamin A in the food on the quantity or fat content of the milk is uncertain, in any case it appears to be much less than that produced by turning the cows out to grass.

3. The increase of the vitamin A-content of the milk produced by feeding cod liver oil is not accompanied by a rise in the lipochrome pigments as is the case when the cows are turned out to grass.

4. Up to 4 ounces per day of a good quality cod liver oil produced no fishy flavour in the milk or butter of one cow, but further experiments appear desirable.

5. Stall feeding even when ensilage was used causes the winter milk to be lower in vitamin-content than summer milk; this is mitigated by such restricted grass feeding as is possible in the south of England.

In an empirical manner cod liver oil has been used for many years as an occasional food for farm animals. Generally speaking, its use has been chiefly confined to the rearing of calves and to improving the condition of horses. It is difficult to glean from the literature of animal husbandry information about the use of this oil, but it would appear that whilst the majority of authorities favour its employment in small amounts in special cases others are inclined to regard the oil with suspicion. Thus, Campbell (1900) (i) recommends cod liver oil as an efficient substitute for cream in the rearing of calves; a conclusion that was confirmed in a later publication from the Leeds Station (Seton, 1901) (2). These reports warn users against the inferior grades of oil and show that if good preparations are used there is no detrimental effect on the flesh when animals are afterwards slaughtered as bullocks.

One of the main problems confronting the advocates of silage in this country is the selection of crops suitable for being grown for ensilage purposes, particularly in view of the fact that attempts to produce maize silage in this country have frequently been unsuccessful. It has been demonstrated, in trials extending over a number of years at Cambridge, that the mixed oat and tare crop can be used for the production of silage with success. The silage from oats and tares, when made under favourable circumstances, is possessed of great palatability and excellent nutritive value, and moreover, the process, considered from the point of view of losses of ingredients as a result of silo fermentation, is, if anything, more economical than that by which maize forage is converted into silage (1).

(1) The ratio of the total lactation yield to the maximum yield, divided by the mean ratio (in the particular district) for the month of calving in which the lactation commenced, has been selected to represent the shape of each individual cow's lactation curve, and has been called the shape figure (S.F.).

(2) The variation of individual S.F.'s was found to be less than that of all cows taken together—i.e. the shape of the curve, though largely determined by environmental factors, is due partly to a genetic characteristic of the cow.

(3) The S.F.'s of 1st calvers are high (about 11 per cent, above those of subsequent lactations); i.e. heifers give a small maximum relative to their total yield.

(4) No significant relation was found between the length of the dry period preceding calving, and the ratio of the total to the maximum yield in the subsequent lactation.

(5) S.F.'s rise markedly and definitely as we pass from low to moderate, and from moderate to high, yielders; i.e. in good milkers the maximum is lower relative to the total yield than in bad milkers. Though there is variation from herd to herd (due probably to the system of management), this rise was shown between bad and good cows within the same herd, and seems to be a definite genetic character.

The initial work on the composition of the fluid obtained from the udders of virgin heifers has been extended and the character of the secretions of the mammary gland during first pregnancy has been investigated.

The results obtained point to the following conclusions:

During the first four or five months of pregnancy, the character and composition of the mammary secretion undergo no essential alterations. During this time, the mechanism of the gland which elaborates the normal constituents of milk is displaying feeble activity.

After about twenty weeks the secretion undergoes a progressive change in character and composition. The characteristic milk constituents begin to disappear, and ultimately the secretion, which is now honey-like in consistency, contains about 40 per cent, total solids, of which about 35 per cent, is globulin. During this phase, which apparently corresponds with a definite stage in the gland's development, the normal activity of the cells which results in the production of caseinogen, lactose, etc. seems to be in abeyance.

Removal of the honey-like secretion from the udder leads to a stimulation of normal mammary gland activity, in the same way as thorough and frequent milking stimulates activity during normal lactation. The viscous secretion gives way to a milk-like fluid. This is produced in relatively large amount and contains appreciable percentages of the normal colostrum corstituents.

If the honey-like secretion is not removed from the gland, the transition from this phase to the eclostral phase appears to be much more gradual and is probably taking place uniformly throughout the remainder of pregnancy.

Whey is the liquid which drains from the curd produced by the action of rennet on milk or from the curd formed by natural souring of milk or by the addition to milk of weak acids or other precipitants.

The concentration of cheese-making at factories in recent years has resulted in the production of large quantities of whey at centres where adequate provision has not been made for its disposal. Part of it is consumed as pig food. The remainder is discharged into streams and sewers. This involves the destruction of large amounts of valuable food material. To prevent contamination, discharge into streams is now generally prohibited. Sometimes it is irrigated on to the land as manure. On the farm practically all the whey produced is consumed as pig food.

It has been shown that the pigment in silage is phaeophytin, the magnesium-free derivative of chlorophyll. It is produced from chlorophyll by the action of carbonic acid and organic acids developed during fermentation in the silo.