THE CAUSATION OF DISEASE. 12$ 



Some very interesting instances of the inheritance of ac- 

 quired characters are on record. Quite recently the Lancet 

 recorded the case of a bitch transmitting to one of its pups a 

 peculiar trick which it had learnt. The pup was removed from 

 its mother while very young, so that the case cannot be ex- 

 plained on the theory of imitation. Similar instances might be 

 recorded by the score. 



There are also on record many cases of the inheritance of 

 obvious tissue-alterations wrought by violent means. Thus, 

 a cow, which had lost a horn from u accident and consequent 

 suppuration," produced three calves which were hornless on 

 the corresponding side, and it is well known that mutilations 

 in man are apt to be inherited, as has happened with injury 

 of the eyes, face, hand, fingers, and other organs. Again, the 

 effects of operations are sometimes inherited : thus, the epilepsy 

 which Brown-Sequard produced artificially in some guinea-pigs 

 by section of the sciatic nerve and injury of the cord, was 

 transmitted to their offspring. The following conditions, arti- 

 ficially induced in the parents, were also transmitted : absence 

 of two or three toes in the hind leg, exophthalmia, haematuria, 

 and dry gangrene of the ears. It is noteworthy that in all 

 these operations the nervous system was markedly involved in 

 the injury ; wherefore, this system has been assumed to play 

 an important part in such inheritances. 



On the other hand, mutilations may be inflicted upon 

 several successive generations without showing the slightest 

 tendency to inheritance. Many savage tribes mutilate their 

 bodies in sundry ways, but, so far as we know, such mutila- 

 tions are never inherited. Moreover, the practice of circum- 

 cision, which has been followed for many generations by the 

 Jews, seems to have left no permanent effect upon the race. 



All this shows us that we have yet much to learn concerning 

 heredity. Yet there can be no doubt that the subtlest changes 

 wrought upon an organism by peculiarities of E tend to be 

 inherited. There is not an act or thought of a parent but 

 may have its effect upon the offspring. What tremendous 

 responsibilities, therefore, rest upon fathers and mothers ! The 

 individual is an embodiment of the hereditary principle. 

 What he is, such future generations springing from him will 



