112 Darwin, and after Darwin. 



result from removal of the cervical ganglia, a droop- 

 ing eyelid from a puncture of the restiform body, 

 a toeless foot from either or both of these opera- 

 tions, and so on? In view of such considerations I 

 cannot deem these suggestions touching " microbes " 

 and " diseases " as worthy of the distinguished 

 biologist from whom they emanate. 



Secondlyj Weismann asks — How can we suppose 

 these results to be instances of the transmission of 

 acquired characters, when from Brown-Sequard's own 

 statement of them it appears that the mutilation 

 itself was not inherited, but only its effects ? Neither 

 in the case of the sciatic nerve, the sympathetic nerve, 

 the cervical ganglion, nor the restiform bodies, was 

 there ever any trace of transmitted injury in the 

 corresponding parts of the offspring ; so that, if the 

 " diseases " from which they suffered be regarded as 

 hereditary, we have to suppose that a consequence 

 was in each case transmitted without the transmis- 

 sion of its cause, which is absurd. But I do not think 

 that this criticism can be deemed of much weight 

 by a physiologist as distinguished from a naturalist. 

 For nothing is more certain to a student of physiology, 

 in any of its branches, than that negative evidence, if 

 yielded by the microscope alone, is most precarious. 

 Therefore it does not need a visible change in the 

 nervous system to be present, in order that the part 

 affected should be functionally weak or incapable : 

 pathology can show numberless cases of nerve- 

 disorder the " structural " causes of which neither 

 the scalpel nor the microscope can detect. So that, 

 if any peculiar form of nerve-disorder is transmitted 

 to progeny, and if it be certain that it has been 



