82 ON HEREDITY. [II. 



loss of fingers, the scars of wounds, etc., are inherited by the 

 offspring, but in these descriptions the previous history is in- 

 variably obscure, and hence the evidence loses all scientific 

 value. 



As a typical example of the scientific value of such cases I 

 may mention the frequently quoted instance of the cow, which 

 lost its left horn from suppuration, induced by some 'unknown 

 cause,' and which afterwards produced two calves with a rudi- 

 mentary left horn in each case. But as Hensen ^ has rightly 

 remarked, the loss of the cow's horn may have arisen from a 

 congenital malformation, which would certainly be transmitted, 

 but which was not an acquired character. 



The only cases worthy of scientific discussion are the well- 

 known experiments upon guinea-pigs, conducted by the French 

 physiologist Brown-Sequard. But the explanation of his results 

 is, in my opinion, open to discussion. In these cases we have 

 to do with the apparent transmission of artificially produced 

 malformations. The division of important nerves, or of the 

 spinal cord, or the removal of parts of the brain, produced 

 certain symptoms which reappeared in the descendants of the 

 mutilated animals. Epilepsy was produced by dividing the 

 great sciatic nerve ; the ear became deformed when the sym- 

 pathetic nerve was severed in the throat ; and prolapsus of 

 the eye-ball followed the removal of a certain part of the brain 

 — the corpora restiformia. All these effects were said to be 

 transmitted to the descendants as far as the fifth or sixth 

 generation. 



But we must inquire whether these cases are really due to 

 heredity and not to simple infection. In the case of epilepsy, 

 at any rate, it is easy to imagine that the passage of some 

 specific organism through the reproductive cells may take 

 place, as in the case of syphilis. We are, however, entirely 

 ignorant of the nature of the former disease. This suggested 

 explanation may not perhaps apply to the other cases : but we 

 must remember that animals which have been subjected to 

 such severe operations upon the nervous system have sustained 

 a great shock, and if they are capable of breeding, it is ovXy 

 probable that they will produce weak descendants, and such as 

 are easily affected by disease. Such a result does not however 



^ ' Physiologic der Zeugung.' 



