Apert: The Laws ov Naudin-Mendel 



497 



distinguish the practice of legal medi- 

 cine from that of clinical medicine. 

 Medico-legal truth demands absolute 

 demonstration: I should take care, for 

 example, in legal medicine, not to af- 

 firm a case of conjugal infidelity, if 

 from the union of two albinos there was 

 born, contrary to the Law of Mendel, a 

 normal child ; we are not yet well enough 

 informed whether, in certain excep- 

 tional cases, extraneous factors may not 

 interfere with the results which would 

 be expected in such a case under the 

 Mendelian Law. 



But in the practice of clinical medi- 

 cine, the case is different. There, we 

 can not act as did the professor in the 

 fable, and philosophize while the child 

 drowns. The possibility of a danger, the 

 probability of a benefit, is enough to 

 give us not only the right, but the duty, 

 of making the appropriate prescription 

 as soon as possible: we thus have a 

 chance of saving from this danger the 

 families whose guidance is entrusted 

 to us, or the hope of benefiting them. 



It is from such a viewpoint that I 

 formulated at the Congress in London 

 some rules * which, in the present status 

 of the science of eugenics, should be 

 considered as allowing us to avoid the 

 dangers to be feared in marriages of 

 members of tainted family stocks, 

 when these taints can be classified as 

 to their mode of inheritance. I persist 

 in thinking that these rules are of great 

 value. For one of the diseases mentioned 

 — albinism — a more rigorous demonstra- 

 tion has proved that they correspond to 

 scientific truth. For the other diseases 

 we have not yet, I admit, anything 

 except a probability based on clinical 

 observation which is often restricted, 

 but often extended. This probability, 

 however, is enough to make it impos- 

 sible for us to disregard the rules which 

 ensure the safeguard of strains of germ- 

 plasm from family diseases. 



* Following are the conclusions of my communication to the Congress of London, where these 

 rules are formulated (they were also published at length in the Monde Medical, 1912, No. 459): 



"To sum up, the study of heredity in family diseases permits us to lay down a certain number 

 of rules which indicate the risks incurred in any given marriage. Such study permits us to 

 withdraw the total prohibition of reproduction, demanded by writers who have studied the 

 question only superficially — a measure too draconian ever to have been enforced. We are now 

 in a position to substitute for such prohibition, advice that is more likely to be followed, because 

 it leaves to the unhappy members of tainted families the possibility of leading a normal life. 



vation verifies the Mendelian propor- 

 tions. 



It seems to me difficult not to admit, 

 as a consequence of these statistics, 

 that albinism in man is recessive and 

 obeys the law of definite proportions, 

 established by Mendel. 



The laws of Naudin and Mendel, 

 then, are incontestably applicable to 

 ^he human species, in this instance. 

 Certainly, that does not prove that 

 they apply equally to other anomalies. 

 I should be very careful about drawing 

 conclusions from this demonstration in 

 albinism, about other family taints in 

 man, whether they be of an anatomical, 

 physiological or pathological nature. 

 There will be no possibility of certitude, 

 until each of these anomalies has been 

 the object of an analogous study. How- 

 ever, if the case for albinism is proved, 

 does it not at least render it probable 

 that other anomalies behave in the 

 same way, and should it not encourage 

 us to pursue our researches in that di- 

 rection ? 



Even before the discovery of the 

 work, we knew that the mode of trans- 

 mission of family defects presented curi- 

 ous partictilars which allowed them to 

 be classed in two groups : Fere proposed 

 the name of fraternal diseases for those 

 in which the heredity is collateral and 

 discontinuous — that is to say, the mode 

 of transmission proper to recessive 

 characters; a second group, parental 

 diseases, is transmitted on the contrary 

 in continuous inheritance, in the manner 

 of dominant characteristics. Is it not 

 very probable that the inheritance of 

 these diseases obeys Mendel's Law, the 

 first being recessives and the second 

 dominants?' Shall we await a rigorous 

 mathematical demonstration before try- 

 ing to make any practical application of 

 the principles which they involve? 



POSSIBILITY OF APPLICATION. 



In this respect, it is important to 



