The Author reports two MZ twin pairs, one of 11 years old females and one of 18 years old males, only one twin in each pair being affected by severe cardiac failure. In both cases the cranial radiograph of the hyposystolic twin, compared with that of the co-twin, revealed the existence of cereblar stasis.

The Author also reports on two female MZ pairs of developmental age, each with one cardiopathic twin. In both cases the affected twin revealed a retarded body development and, in one pair, also retarded puberty.

The Author stresses how the twin study method is helpful in clinical as well as genetical research, thus reasserting its validity.

Roentgenograms have been taken of the hand and wrist on 58 pairs of MZ twins, on 40 pairs of DZ twins, and on 4 groups of triplets, between 2 and 18 years of age.

Their comparative examination has shown the highest concordance in MZ pairs and a remarkable discordance in DZ pairs, accentuated above all in those of opposed sex. Generally, the comparison between male and female pairs of same age has shown a delay on bony growth of the firsts, event remarkable also within DZ pairs of opposed sex.

Comparing the Roentgenograms taken with those standard of Greulich and Pyle, generally it is to be remarked that males are retarded in regard to females.

Some cases of concordant paramorphysms in healthy pairs of MZ twins and of remarkable immaturity in MZ pairs at the same time sick are also shown.

The Autors analize 25 families with proband affected by thromboangiitis obliterans, 25 families with proband with periferal arteriosclerosis obliterans and 300 families with proband with infectious diseases. The last two groups are as controll.

After describing two cases of thromboangiitis obliterans on the families of proband with T. O., the AA. examine the material under the statistical point of view.

In the group of families with T. O. they founf on higher incidence statistically signifiant, of rheumatic diseases (rheumatic fever and rheumatoid arthritis) and cerebral apoplexy of early unset (before 55 years of age).

The AA. admitt the existence of a genetic predisposition to thromboangiitis obliterans.

Such a predisposition probably leads on two genetic factors: one dominant autosomal with reduced penetrance and variable expressivity, witch is responsable of the abnormal mesenchimal reactivity (and for sue a reason, strictly related to the principal factor responsable of the predisposition to rheumatic disease). Tre other, recessive one, is responsable of a state of vascular vulnerability. This last factor is probably the localizing factor of the abnormal responsivity to the vascular mesenchima.

The genetic predisposition to rheumatic diseases, in the other way seems to have non genetic relationship to the diathesis of allergic diseases and the diathesis of degenerative connective tissue disorders (mesenchymotic diathesis).

The history of the development of knowledge of the Rh-Hr types is briefly reviewed, with special reference to the theory of multiple allelic genes. It is pointed out that this theory has been confirmed by numerous statistical studies of the Rh-Hr types in the population as well as extensive studies on families. In addition to corroborating the genetic theory, the newer studies have disclosed the great complexity of this blood group system, so that as many as 20 allelic genes have been identified up to the present time. In the case of the more common genes there is ample direct evidence to verify the genetic theory, but observations on the rarer blood types are necessarily limited, so that the validity of the genetic theory, as it pertains to the rarer Rh genes, is based mainly on analogy. In this paper, two unusual families are recorded, which illustrate the hereditary transmission of the rare agglutinogens rh′w and Rhz. These observations serve to justify the inference that the rarer Rh genes are subject to the same laws of heredity as the more common alleles of the Rh-Hr allelic series.

The object of this study was to ascertain if endogenous factors might play a part in the appearance of paralysis with acuta anterior poliomyelitis.

The investigation concerned 754 patients in Groningen and Drenthe (provinces of the Netherlands), affected by the disease during the years 1936-1951. First of all it appeared that the consanguinity percentage of the parents of the probandi was much higher than that of the average population the difference being significant (χ2 = 22,28; P: 〈0.001). Secondly we compared the number of connections of a group of 137 patients with a group of 591 patients and the number of connections of a control group of 137 persons with the group of 591 patients. As ignificant difference appeared to exist between the numbers observed. The third part of the research concerned the appearence of diseases with patients' relatives and the comparison of those with the diseases with relatives of a control group. Between the group of patients and relatives and the group of control cases and relatives a difference appeared to exist in this sense that in each case the group first-mentioned showed a “surplus” of diseases in comparision with the control group; the burdening of the poliomyelitis-group with these diseases showed a significant difference from that of the control group. Also in this case the comparison of several separate diseases showed significant differences. However this was not the case with all the diseases. Attention was paid to the twins who occurred in the group of 754 patients. The small number of twins, however, did not allow of any conclusion whatsoever.

Finally the conclusion has been drawn, that endogenous factors exercise influence in the origin of paralysis with acute anterior poliomyelitis. The results of this investigation render it probable that we have to deal with a non-specific factor, viz. a greater vulnerability of the central nervous system for diverse diseases of which the increased susceptibility of the paralytic form of acute anterior poliomyelitis forms a part.

This factor is inherited in a recessive way.

The problem of the familial incidence of cancer has been studied on the basis of the genetical researches of the last ten years on leukemia, cancer of the breast, uterus, prostate, bladder and stomach. The conclusion has been reached, except for the cancer of the bladder, of the existence of a significant familial incidence of cancers.

Examinations of 92 monozygotic and 83 dizygotic twin pairs and 27 families with 78 children have given the result that the ability « tongue curling » is to a certain degree, but not exclusively hereditary. Furthermore, some people are able to learn it. Hence, it is not an unconditionally constant individual trait. By a somewhat more exact functional analysis it is shown that the alternative distribution in the population is counterfeinted only. Hence, there is no evidence for the monomere inheritance lati in Groningen e Drenthe (due supposed by some authors.

By cytological diagnosis of chromosomal sex it has been shown, that about 80 per cent of all cases of gonadal dysgenesis are genetically male. In about 8 per cent of male individuals various defects of red-green sensitivity may be expected. Deuteranopia was observed in a hetero-gametic pseudo-female with testicular dysgenesis. Tests for colour vision should be made in all patients with the syndrome of testicular feminization. From such tests a decision may be expected between sex- linked recessive and autosomal dominant transmission with sex limitation.

Two cases are reported of MZ twin pairs with a history of retarded speech and universal stammering followed by concordant agrammatism.

A survey of a number of twin pairs reveals, however, discordance in speech development, in stammering and in language proficiency: agrammatism is, therefore, e genotypical trait.