V 



PREFACE. 



I WENT to Leipsic in 1874 to Ludwig's Laboratory with 

 the intention of working at problems connected with the 

 sympathetic nervous system, and from that time until now 

 my thoughts have been occupied with the meaning of this 

 nervous system and with problems which have arisen from 

 its study, such as the origin of the vertebrate central 

 nervous system and thence the origin of the vertebrates 

 themselves. 



On my return to England, at the request of Professor 

 Foster, I gave some lectures on the innervation of the 

 vascular system, which led to a course of lectures on the 

 sympathetic and allied systems of nerves. These lectures 

 have been continued from year to year up to the present 

 time, and at the request of some of my past students I 

 have determined to publish an epitome of them in book 

 form, in order to put before the world the part which my 

 researches have played in the elucidation of the problems 

 concerned with the innervation of involuntary muscular 

 systems. I am especially inclined to do this now, because 

 recent researches have thrown so much light on the origin 

 of the cells of the sympathetic nervous system and their 

 close relations with the chromaffine cells, that I am able 

 to present to my readers a consistent and harmonious 

 account of the plan of innervation of all the involuntary 

 muscular systems in the higher vertebrates both from a 

 physiological and from a morphological point of view. I 

 have been guided throughout all the investigations I have 

 ever made by the feeling that the broader physiological 



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