60 NERVOUS SYSTEM. 



defined, frequently presenting concentric laminae and a hilum. 

 When carefully treated, first with a solution of iodine and then 

 with a little sulphuric acid, they assume a blue color. Some 

 observers consider them as analogous to cellulose, others have 

 supposed that they are formed of cholesterine, and others 

 regard them as nitrogenized bodies. * These points are of 

 purely anatomical interest, and the physiological relations 

 of these bodies are not known. 



Regeneration of the Nervous Tissue. 



"We do not propose to discuss fully the question of the 

 regeneration of nerves after section or even excision of a 

 portion of their substance, though it is one of great patho- 

 logical interest ; but in this connection will refer to some 

 experiments recently made, in which it appears that it is pos- 

 sible for certain of the most important of the nerve-centres 

 to be regenerated and their function restored after extir- 

 pation. 



"With regard to the simple reunion of nerves after division 

 or excision, it has long been known that this takes place in 

 the human subject and in the inferior animals, with restora- 

 tion of function. 3 The new tissue connecting the divided 

 extremities of the nerve seems to pass through the regular 

 stages of development observed in the nerve-tissue of the 

 embryon, the gelatinous fibres, or the fibres of Remak, first 

 appearing, and these being subsequently developed into true 

 nerve-tubes. In this process there is not a cicatrix, as in 

 the skin or muscular tissue, but a development of new ele- 

 ments possessing the anatomical and physiological charac- 

 ters of the original structure. 



1 VIRCHOW, he. tit. 



LITTRK ET ROBIN, Dictionnaire de medecine, Paris, 1865, Article, Cor- 

 puscle. 



2 LAVERAN, Recherches experimentales sur la regeneration des nerfs, These, 

 Strasbourg, 1867. This memoir contains an elaborate review of the earlier ex- 

 periments upon the regeneration of nerves, with some original observations of 

 much interest. 



