82 ON HEREDITY. 



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 sympathetic 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 here- 

 dity 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 only probable that they will produce 

 weak descendants, and such as are easily affected by disease. Such 

 a result does not however explain why the offspring should suffer 

 from the same disease as that which was artificially induced in 

 the parents. But this does not appear to have been by any means 

 invariably the case. Brown-Sequard himself says, ' The changes 

 in the eye of the offspring were of a very variable nature, and 

 were only occasionally exactly similar to those observed in the 

 parents.' 



There is no doubt, however, that these experiments demand 

 careful consideration, but before they can claim scientific recogni- 

 tion, they must be subjected to rigid criticism as to the precautions 

 taken, the number and nature of the control experiments, etc. 



Up to the present time such necessary conditions have not been 

 sufficiently observed. The recent experiments themselves are only 

 described in short preliminary notices, which, as regards their accu- 

 racy, the possibility of mistake, the precautions taken, and the exac-t, 

 succession of individuals affected, afford no data upon which a 

 scientific opinion can be founded. Until the publication of a com- 

 plete series of experiments, we must say with Du Bois Reymond 1 , 

 1 The hereditary transmission of acquired characters remains an 

 1 See 'Ueber die Uebung,' Berlin, iSSi. 



