Pharmacogenetics represents a field of connection and cooperation between pharmacology and genetics, which will promote knowledge in both fields. It concerns the plusvariant action of drugs in those families in which they produce toxic reactions, as well as the minusvariant action in particularly resistant families, so that drugs become useless at normal doses. These phenomena stress both the mechanism of action of such drugs and the existence of hereditary metabolic defects. Some typical cases are reported, with special concern to twin observations. It is finally suggested that pharmacogenetics may concern three specific branches: (a) regulation, (b) substitution and (c) repair.

After a historical review of the problem of progressive myoclonic epilepsy, the author makes a detailed clinical and genetic description of 5 families from the Valais canton, affected with the disease. The metabolic disturbances observed in these cases (urinary elimination of mucopolysaccharides) are given particular attention. The author further discusses the various classifications of myoclonic epilepsy which were established on the basis of clinical symptomatology, electroencephalographic tracings, pathological anatomy and biochemical findings.

The distribution of G6PD-D in the Ferrara country has been studied by means of the Brilliant Cresyl Blue discoloration test: 2437 males have been tested in 11 localities.

The highest gene frequency of G6PD-D observed is consistent with the one expected after 25-30 generations of malaria selection, assuming an increased fitness of the heterozygotes, as it has been shown in computer simulated evolutionary trends for sex-linked genes. The thalassemia trait has also been shown to be very frequent in the same localities; its frequency is correlated with G6PD-D gene frequency and with the incidence of malaria in the past (1900).

G6PD-D frequency is not significantly correlated with malaria. Such a result is due to the significantly lower gene frequency of G6PD-D observed in the localities where the percentage of population affected by malaria was higher (40-60%). On the other hand, G6PD-D is frequently significantly correlated with malaria in the remaining localities where the incidence of the latter ranged from 0 to 35% of the affected population.

The mechanisms possibly involved in the determination of this distribution of G6PD-D are discussed.

General formulae for the chances of excluding paternity by blood grouping tests have been derived for the case where the falsely accused man is dead, but both his parents are available for testing. With the aid of the formulae, the chances of excluding paternity are shown to be about 31.1%, when tests are carried out for the A-B-O blood groups and subgroups, the M-N types, the Rh-Hr types and the Kell factor. These combined chances are about half the chances of exclusion when the putative father is alive and can be tested, so that it is very much worth while to carry out blood grouping tests in cases of this nature.

The present paper deals with an analysis of the statistics concerning twin births in a sample of the Belgian population in 1960 and 1961. The frequency of twin births is of 0.01198 (± 0.00043), the frequency of a DZ birth among twins is 0.65081. Mothers of twins generally are older than mothers with children resulting from single gestation, the age difference concerning, as could be demonstrated, the distribution of DZ twins with the exclusion of MZ twins: whereas the frequencies of the total amount of twin births and of the total amount of DZ births increase with the mother's age, being highest in the 35-39 age class, the frequency of MZ births seems to be independent of the mother's age. The frequency of twin births also increases with the order of birth or gestation. Given that the mother's age and the order of birth are correlated, the influence of one of the two factors involved upon the frequency of twin births could be determined by keeping the other factor constant; the data from Mac Arthur (1953) were used to that effect.

Finally, a bibliographic survey revealed that whereas the frequency of DZ births is very variable, that of MZ births is more constant.