HuBER, Sympathetic Nervous System. 75 



until more was known concerning the structural elements con- 

 stituting this system. The fact that the sympathetic is made 

 up of nerve cells and nerve fibers, as is the brain and cord, was 

 known to these earlier writers. That its nerves seemed struc- 

 turally different was also known. Yet their views concerning 

 the relation of sympathetic nerve fibers to the sympathetic cells, 

 the endings of these fibers in the tissues to which they had been 

 traced, and the relation of sympathetic cells and fibers to the 

 cerebro-spinal system, were based on opinions obtained only in 

 part by observation, speculation often playing an important 

 role. This of course is not at all surprising when we consider 

 the imperfect histological methods known to these pioneer in- 

 vestigators, for it must be remembered that it is only a little 

 more than three decades since Gerlach discovered that solutions 

 of carmine would stain effectively animal tissues. 



Our knowledge of the ultimate structure of the nervous 

 system taken as a whole has in the last twenty years been 

 greatly extended by the results obtained through the applica- 

 tion of new and improved methods of microscopical technique. 

 It is however not my purpose to mention even briefly all the 

 neurological methods which have thus materially aided in the 

 furtherance of our knowledge. I deem it profitable howevier 

 to draw your attention to two methods, consequent upon the 

 application of which, more than upon all other methods, has 

 the elucidation of the difficult problem here involved been pos- 

 sible. One of these methods was suggested by Golgi (3) in 1875, 

 who found that nerve tissues prefixed in a solution of bichro- 

 mate of potash and after-treated with silver nitrate, would take 

 a most delicate stain, the nerve cells with all their branches, 

 even to their finest details being most clearly portrayed. This 

 method has become especially valuable since Ramon y Cajal 

 has demonstrated that it is especially applicable to embryonic 

 tissues, even in the very early stages of the developing embryo, 

 where the structural appearances are often somewhat simpler 

 and more amenable to a correct interpretation. The other 

 method, of more recent origin, was suggested by Ehrlich (4) in 

 1886. Ehrlich found that by injecting a solution of methylen- 



