ON HEREDITY IN NERVOUS DISEASES. 335 



Those young can be allowed to breed in-and-in, and always the 

 same phenomena will be observed in each subsequent generation. I 

 have sometimes noticed that if a male or a female belonging to any 

 one of tlie successive generations is allowed to breed with another 

 healthy animal, very generally some of the young present the same 

 hereditary peculiarities. I have followed animals thus operated upon 

 through seven generations. 



But what is still more remarkable is the transmission of an epilep- 

 tic malady artificially induced. Dr. Brown-Sequard, as is well known, 

 has for nearly thirty years made experiments on this subject of epi- 

 lepsy, and his researches have discovered an array of facts of the high- 

 est value, to lighten the obscurity which has at all times rendered 

 the true causes of that disease unattainable. He has made the like 

 of what renders illustrious the names of the foster-fathers of experi- 

 mental physiology a synthesis : he has produced an epileptic malady 

 in the Guinea-pig, which presents all the characteristics observed in 

 tliat disease in the human species. 



Dr. Brown-Sequard found that when the spinal cord of a Guinea- 

 pig is pricked, or a portion of it is destroyed, or one of the sciatic 

 nerves that is, one of the largest nerves of the hind-leg is either 

 sectioned or torn off from the spinal cord, the animal in the course 

 of a few weeks develops the epileptic malady. First, after a week 

 or a little more, all traces of the operation have disappeared, as far as 

 the wound is concerned. When the spinal cord has been operated 

 upon, sometimes the feeling of pain is found lacking to a slight de- 

 gree on the opposite side, and exaggerated below the point of the 

 body at which the wound has been made ; but most generally no such 

 symptoms at all exist. 



When the sciatic nerve has been cut or torn away, the greater 

 portion of the leg is paralyzed as to motion and sensation, which 

 is natural enough, because the muscles can no longer obey the man- 

 dates of the will, being deprived of the nerves which carry them, 

 and also the centres no longer receive impressions which formerly 

 came from those muscles and the skin covering them, because the 

 nerves which carry the impressions have been destroyed. 



It happens, also, in this case, that those parts which are thus de- 

 prived of motion and of sensation are dragged on the ground, are 

 easily hurt, and become inflamed and enlarged. As soon as the skin 

 has been broken, the animal begins to eat away all the parts of its 

 leg which it does not feel ; but it cautiously stops at the very 

 limit where sensation still persists, so that, as, out of its three toes 

 which terminate its posterior limb, the inner one is animated by 

 nerves which do not come from the sciatic, that one toe has pre- 

 served sensation and motion. Therefore, when all the insensible tis- 

 sues have disappeared, the wound heals very rapidly, and the animal 

 has a limb which terminates by one toe only, the inner. 



