364 ACTION OF NATURAL SELECTION 



of the ear or partial closure of the eyelids. Dr. Leonard 

 Hill* has also repeated them with some thoroughness. 

 The operation was performed on six guinea-pigs, and 

 these animals were allowed to interbreed. It was 

 again performed on twelve of their offspring, and these 

 were also allowed to interbreed, but none of the young 

 of either the first or the second generation showed any 

 persistent droop of the eyelid. Hill found, however, 

 that many of the young guinea-pigs exhibited a partial 

 closure of the eye for some time after birth, but this 

 phenomenon was due entirely to conjunctivitis, the re- 

 sult of dirt getting into the eyes. It affected both eyes 

 equally often, and when it terminated the droop disap- 

 peared also. One is strongly tempted to conclude that 

 the partial closure of the eyelids observed by Brown- 

 Sequard was due to a similar cause, and was no more 

 hereditary than in Hill's guinea-pigs. Certain of 

 Brown-Sequard's experiments have, however, been cor- 

 roborated by subsequent observers, and must therefore 

 be accepted. Thus he found that animals which had 

 been rendered epileptic by injury to the spinal cord, or 

 section of the sciatic nerve, might transmit this epilepsy 

 to their offspring. These results have been confirmed 

 by Obersteiner,f and Westphal has even succeeded in 

 producing epilepsy, which was transmitted to the off- 

 spring, by striking guinea-pigs on the head with a ham- 

 mer. It has been suggested by Weismann that the 

 transmission might be due to the introduction of some 

 microbe into the operative wound, which both caused 

 epilepsy in the parent, and, by invading the germ cells, 



* Proc. Zool. Soc. 1896, p. 785. 



f Oesterreichische medicinische Jahrbiicher, 1875, p. 179. 



