52 Experimental Zoology 



I do not propose to consider in detail the cases that Darwin 

 and Spencer have brought forward (most of them will not bear 

 critical examination, as Weismann has so ably shown), but, as 

 has been said, I shall consider rather those cases, most of them 

 recent, in which attempts have been made by direct experiment 

 to show that acquired characters are inherited. 



The work that has attracted most attention is that of Brown- 

 Sequard. A full statement of Brown- Sequard's experiments and 

 results is given by Romanes in his book "Darwin and After 

 Darwin," Vol. II, Chap. IV. The experiments were m.ade 

 with guinea pigs. Epilepsy was induced by operations on 

 some part of the nervous system. The young of these animals 

 sometimes developed epilepsy, or some of its effects, in the same 

 part of the body as that affected in the parent. The details of 

 the experiments are as follows : The parents became epi- 

 leptic after injury to the spinal cord or by section of the sciatic 

 nerve. The "epileptiform habit" does not supervene until 

 some time after the operation and lasts only "for some weeks 

 or months." The convulsions "never occur spontaneously, 

 but only as a result of irritating a small area of skin behind the 

 ear on the same side of the body as that on which the sciatic 

 nerve had been divided." ^ The attack lasts only a few minutes, 

 and during this time the animal is unconscious and convulsed. 

 The habit is only rarely transmitted to the young, but as the 

 disease occurs only in guinea pigs whose parents have been 

 made epileptic by an operation of the sort described above, 

 and never in the young of guinea pigs that have been operated 

 on in other ways, there seems to be here something more than 

 a coincidence. 



Another series of experiments consisted in cutting the cervi- 

 cal sympathetic nerve. This operation causes a change in the 

 shape of the ear, and a similar change is said to appear in the 

 young. By cutting the cervical sympathetic nerve or by re- 

 moving the superior cervical ganglion, the eyelids partially 

 close, and this closure was also seen in the young. 



^ Romanes, "Darwin and After Darwin," II, 1895. 



