SPECIAL PHYSIOLOGY. 43 



taken more or less part in the formation of the white pos- 

 terior columns, they then join the gray substance. Thus it may 

 be said that sensibility traverses the posterior roots, the pos- 

 terior columns, and the gray substance : this last seems more 

 particularly endowed with the conduction of painful sensa- 

 tions, and the posterior columns to the sensations of touch or 

 contact. In fact, by experimentation each of these modes of 

 sensation can be destroyed, and they are perfectly isolated 

 by the state of chloroformization (or etherization). An ani- 

 mal whose gray axis alone has been bisected, or which has 

 been subjected to the action of chloroform, loses sensation of 

 pain, but yet all the tactile sensations may be carried to the 

 brain. The centrifugal nerves form the antero-lateral columns, 

 and then leave the spinal cord by the anterior roots of the 

 spinal nerves ; these roots start from the gray substance of 

 the cord. So the white substance of the cord is formed by 

 the nerve roots that go through this spinal cord in a more or 

 less oblique direction, and also by vertical fibres (properly 

 called columns), the whole enclosed in a peculiar uniting 

 substance, which German histologists consider to be the em- 

 bryonic form of the connective tissue. 1 



The knowledge of the centrifugal functions of the antero-. 

 lateral column and of the anterior roots, of the centripetal 

 functions of the posterior roots and of the posterior columns, 

 form the essential points of the physiology of the spinal cord; 

 but in order to satisfy the demands of pathology, and for an 

 explanation of the numerous facts discovered by vivisections 

 and the study of the degenerations of the fibres of the spinal, 

 physiology should seek for a solution of the following ques- 

 tions : What is the object of the connective tissue in the struct- 

 ure of the spinal cord ? What is the direction of the fibres 

 of the roots? Do these go directly to the encephalon, or do 

 they terminate in the cells of the spinal cord ? Are the fasci- 

 culi of the cord as excitable as the nerves? Do these follow 

 an ascending or descending course, or do they cross from one 

 side of the cord to the other? 



Neuroglia, a kind of connective tissue in the spinal cord, 

 adopting the explanation of Virchow (op. cit. pp. 71, et seq.) 

 has been the especial study of anatomists belonging to the 

 school at Dorpat, who, moreover, have perhaps slightly 

 exaggerated its importance (Owsjanikow, Metzler, Kupffer, 



1 Neuroglia, or nerve cement. Virchow's " Cellular Pathology," 

 .translated by Chance, Am. ed., p. 315. 



