304 PROGRESS OF SCIENCE IN THE CENTURY. 



nerves instead of to the nerve-centres with which they 

 are associated. 



It was recognised by Vulpian (1866) that "all 

 nerves sensory, motor, vaso-motor, and others 

 have the same properties, and are only distinct in 

 their effects. This question is of the highest impor- 

 tance for general physiology. It dominates the whole 

 physiology of nerve-fibres." * " Many observations 

 made since Vulpian wrote have shown that a nerve 

 has no functions more specific than those of a tele- 

 graph wire. It conducts impulses and is incapable 

 of tampering with the messages which it trans- 

 mits." f 



Since the days of Miiller the progress of this de- 

 partment of physiology has depended on work along 

 several distinct lines. There is, on the one hand, 

 the more experimental method which aims mainly at 

 localising certain functions in certain parts of the 

 system; from Willis and Flourens (1794-1864) 

 among the early workers, to Ferrier, Eritsch, Hitzig, 

 Munk, Goltz, and Horsley, there has been a remark- 

 able record of achievement. This has depended 

 partly on experimentation with living creatures, and 

 partly on the observation of pathological conditions, 

 i.e., on the correlation of abnormal functions studied 

 during life with the abnormal structure revealed on 

 post-mortem examination. 



There is, on the other hand, the histological path 

 " the attempt by microscopic analysis to find a way 

 through the extraordinary maze of cells and fibres 

 which form the brain and spinal cord. Albert von 



* Quoted by Dr. Alex. Hill. Introduction to Science, 1900, 

 p. 118. 



id., p. 118. 



