GENERAL ANATOMY. 



the ganglions, a peculiar gray substance, traversed by white 

 fibres; finally, in the nerves white fibres alone. 



The white substance alone forms a continuous whole. The 

 gray substance, on the contrary, is only met with at intervals; 

 it is found especially where the central extremities of the 

 nerves are inserted; it has been supposed even to exist at 

 their peripheral extremities, and especially in the corpus mu~ 

 cosum of the skin; it is found also where the white fibres in- 

 crease and seem to expand, as in the crura cerebri and cerebel- 

 li; finally, it is found at the surface of the brain and cerebel- 

 lum; it has been thought even, but without proof, that it ex- 

 isted in the ganglions. 



The fibrous texture of the nervous substance had been for- 

 merly observed in the white substance by Malpighi, but he 

 regarded the gray substance as glandular. 



This idea of Malpighi respecting the gray substance, has 

 been for a long time admitted in conjunction with the hypo- 

 thetical opinion that the nerves are hollow or canaliculated. 

 Afterwards, this idea of Malpighi, respecting the gray sub- 

 stance, gave place to that of a point of origin (Gall,) and of a 

 centre of action, (Ludwig,) &c. 



749. The nervous substance, whether white or gray, on 

 being examined with the microscope,* and enlarged about 

 three hundred diameters, appears in all its parts composed of 

 semi-diaphanous globules, united by a transparent arid viscous 

 substance. These globules have appeared to Delatorre differ- 

 ent in size in the brain, cerebellum, spinal marrow, and nerves, 

 the largest being in the brain, and the smallest in the nerves; 

 these globules have appeared to him heaped together without 

 order in the central nervous mass, and in linear series in the 

 nerves; as to the liquid in which they are contained, it appear- 

 ed to him slightly viscous in the encephalon, more so in the 

 spinal marrow, and still more so in the nerves. These glo- 

 bules, and the liquid which surrounds them, furnished and re- 



* J. M. Dellatorre, Nuove osserv. micros.; in Napoli, 1776. Prochaska de 

 struct, nervor. J. and Ch. Wenzell, dePenitiori struct, cerebri; Tubing 1 . 

 1812. A. Barba, Osserv. microsc. sul ccrvello e suite parti adjaccnti; Napoli 

 1807. Home and Bauec, Philos. Trans.; ann. 1821. 



