10 Eugenics Record Office, Buli,etin No. 3 



to get the law of inheritance from a single family, and the practice had 

 been to lump the data, and say, for example, that in one hundred cases of 

 insanity, a distinct inheritance was found in 35. This method of lumping 

 the data had not been generally satisfactory, and of no practical use in 

 predicting what would be the outcome of the children of a particular 

 mating, nor was it of any particular value in explaining how a particular 

 insane patient came to exist. The present method avoided this massing 

 of the data by boldly attacking each family, and recognizing that the 

 insanity was due to a particular combination of maternal and paternal 

 germ-plasms. This gave an entirely different value to the study of 

 heredity and enabled us to say that a particular mating would necessarily 

 give rise to such and such a proportion of insane offspring, or that a 

 certain insane patient must have had insanity in both the maternal and 

 paternal germ-plasms. 



One remarkable fact that had been brought out was the close relation- 

 ship between different forms of amentia — dementia praecox, manic-depres- 

 sive insanity, senile dementia do not depend on the absence of different 

 kinds of units. The same rules of inheritance held good for epilepsy and 

 feeblemindedness, namely, that two feeble-minded parents could have 

 only feeble-minded offspring, and that two epileptic parents could have 

 only feeble-minded or epileptic offspring. Many of the statistics which 

 had been collected hitherto did not bear, as they had been thought to bear, 

 upon the question of causation of these various mental defects. For 

 example, statistics had been collected upon the alcoholic habits of the 

 parents, upon their nutritional defects and clinical history, but we now 

 knew that no matter under what conditions the children were bom, 

 whether under favorable or unfavorable conditions, the statistical results 

 remained practically constant and the same. 



As to the relation between heredity and environment, the question 

 was often asked, did the latter play any part at all in determining the 

 onset of mental disease? In the case of the feeble-minded it seemed that 

 environment did play a small part : in the case of insanity, a larger part. 

 Both environment and the neuropathic condition of the protoplasm were 

 active factors in the production of insanity. An unfavorable environment, 

 falling upon an individual with an inherited weakness, resulted in a mental 

 breakdown. The result was always due to the combination of the environ- 

 ment and the protoplasm. The disease itself was not inherited; only the 

 weakness, and the disease made its appearance only when some stress of 

 life fell upon such a weak protoplasm. Then the protoplasm showed its 

 weakness, and the individual succumbed. 



Dr. B. Onuf said the valuable paper of Drs. Cannon and Rosanoff, 

 while largely theoretical, had also practical aspects. Any one of us might 

 be confronted with the question of whether, under given conditions of 

 ancestry, certain persons should contract marriage. Naturally, our answer 

 to such a question had usually been quite vague. If the investigations 

 made by the authors of this paper, which he understood was only a 

 preliminary report, were corroborated by further statistics, then our knowl- 

 edge of heredity would become clearer and better defined and enable us 

 to give correspondingly clearer answers to the inquiries mentioned. 



Dr. Onuf referred to the fact that certain psychoses seemed to occur 

 within well-defined lines. Thus, manic depressive insanity was very apt 

 to occur in families, and paranoid conditions on the other hand were often 

 associated with an ancestral history of paranoid disease. Certain types 

 of convolutions had been found to occur in succeeding generations. 



