The Authors show twin study to allow the determination of gene frequency and penetrance in the general population, by means of the analysis of distribution of phenotypic combinations in the twin pairs.

In order to test the possible effect of maternal inbreeding upon non-disjunction, ancestors of 104 children with Down's syndrome born to younger mothers were identified on the basis of official records. Among them, 6 had related parents, while 10 of the fathers and 12 of the mothers had also such parents. The relationship comprises first-cousins, first-cousins once removed, and second cousins. It was concluded that recessive genes are unlikely to be involved in the aetiology of non-disjunction of the 21st autosome, at least in younger mothers.

The Authors studied the leukocyte alkaline phosphatase (LAP) activity in 40 subjects with Down's syndrome. The age of the patients ranged from one week to 15 years. Chromosome analysis was carried out in 13 cases. 42 normal children of the same age as the patients were used as controls. The mean value of LAP in the patients with Down's syndrome was 175.5 and in the control group 108.8. In the latter group the LAP activity was clearly influenced by the age; the highest values were obtained in children under 11 years of age. The regression coefficient of the LAP on the age in the control group was –3.73. In the patients with Down's syndrome the differences observed between the various age groups were not statistically significant.

Chromosome studies showed a 21 trisomy in 12 cases; in one case a 15/21 translocation was found. The latter case presented an elevated LAP activity.

The Authors support the hypothesis that the gene or genes controlling LAP activity are located in the 21 chromosome and that the LAP activity may vary under the influence of several factors within the limits of the genetic control.

The Authors describe a pedigree including four certain and two probable cases of «Ehlers-Danlos syndrome ». All the affected subjects were born to consanguineous but apparently healthy parents. Of the three main symptoms of the syndrome, the patients presented hyperelasticity of the skin and hyperlaxity of the joints and of the ligaments, while the signs of cutaneous fragility were absent (« partial form » of E.-D. syndrome). In the first two cases it was possible to find some less common aspects of the E.-D. syndrome, such as ectasia of the trachea and of the main bronchi, anomalies regarding the eyes, the teeth and the nails, muscular hypotonia and hypotrophia, and particularly some skeletal manifestations (bending of the long bones, osteoporosis, anomalies of the methaphysis and epiphysis of the tubular bones, vertebral, thoracic and pelvic deformations).

The Authors emphasize the importance of these less common aspects of the E.-D. syndrome, and the similarity between these clinical signs and those found in other « heritable disorders of the connective tissue ».

The type of inheritance in this family (autosomal recessive) is discussed, in comparison to the commoner type (autosomal dominant) of inheritance of the E.-D. syndrome.

A description is made of a Brazilian family of white ancestry in which five individuals presented the fibrous dysplasia of the jaws known as cherubism. The information obtained involves seven generations in a total of 75 individuals. 23 of these were examined by the authors and a report about a deceased person was confirmed by photograph. The affection in this family is probably conditioned by an autosomal dominant gene with variable expressivity.

After a brief introduction on the genetic aspects of serum Cholinesterase, the Authors describe two familial cases of subjects homozygous for the atypical gene of Cholinesterase, who had severe apnoea following anesthesia.

The results are presented of a study of ulnar loops in complete or partial symmetrical formulae, in all possible combinations, in a sample of 200 families taken at random in the population of Montevideo.

Some partial formulae not only appear in a significantly higher proportion when both parents have them, and in a smaller amount when they lack them, but also seem to be inherited in a higher degree than the theoretical expectancy of the combined chances of the patterns they are made up of.

The authors' conclusions is that there seems to be a basic influence of factors determining the inheritance of independent patterns, plus a second one, resulting from the meeting of some patterns to give a more remarkable genetic effect for the inheritance of partial formulae.

1. The author has worked out a new systematics for the interdigital patterns of the palm based on the building up of digital triradius 3 and the extension of main line C with the following types of pattern as result: U (ulnar loops), R (radial loops), O (open-field pattern) and V (vestiges — incomplete patterns or “special” patterns).

2. A significant difference in frequency for the pattern distribution between the two hands has been found for U, R as well as for O-patterns (U-patterns and O-patterns appear with 6.5 respectively 14.3% higher frequency on the left hand, while R-patterns appear with 20.2% higher frequency on the right hand.).

3. The pattern distribution does not show any difference between the two sexes.

4. Calculations of correlations in tetrachoric tables have shown a strong mother-child correlation on the 99.9% level for U-pattern set against R-pattern for both the right and the left hand (r = 0.39-0.43).

The South Indian populations differ from one another for the frequency of hairy ear rims, tragus hair and hairs on the ear lobe. The difference in the age of onset is not very striking. Whether they are due to the same gene, or genes, or to independent genes, cannot be answered until detailed pedigree studies are made.