SYMPATHETIC NERVE. 



453 



of an inch in diameter, and presenting 

 a slightly granular surface (most of them are 

 round ; others have more or less an oval 

 shape) ; 2nd, distinct cells measuring from 

 the TTjtarth to the T 2Vo tn f an lncn U1 ( ' ia " 

 meter : they contain a finely molecular fluid, 

 and also a nucleus. The latter, which is fre- 

 quently situated towards one side of the cell, 

 is round and granular, and generally contains a 

 nucleolus. With the exception of their smaller 

 size, they resemble ordinary ganglionic cor- 

 puscles. The nerves in the ganglion present 

 the aspect of flattened bands of blastema, 

 consisting almost entirely of corpuscles re- 

 sembling those first described, arranged close 

 together in linear series in a somewhat gra- 

 nular matrix. They vary in breadth consi- 

 derably. The ganglia on the posterior roots 

 of the spinal nerves present the same struc- 

 ture. 



The sympathetic ganglia appear to be en- 

 tirely composed of structures similar to those 

 first described, imbedded in a more or less 

 granular transparent blastema. 



In embryos of 6 to 8 inches in length, the 

 sympathetic ganglia still contain a large num- 



A, Ganglion- corpuscles from the Gasserian gan- 

 glion of a calf 7 inches long; B, nerve-fibres from 

 the brachial plexus of the same animal ; c, from 

 the superior cervical ganglion of the sympathetic ; 

 D, nerve-fibres from the main cord of the sympathe- 

 tic in the thorax. 



ber of corpuscles similar to those in earlier 

 embryos. There are also present a number 

 of bodies larger than these, and consisting of 

 a distinct cell-wall inclosing, besides a nucleus, 

 a finely-granular fluid. They are commonly 

 round ; some are more or less eiig-shapcd. 

 The nucleus in the latter is generally situated 

 towards the wider extremity of the eel 1 , while 

 its narrow end is prolonged into a delicate, 

 granular process about the -s^tyth of an 

 inch in breadth. The nerves in the gan- 

 glia do not differ much in appearance from 

 those in the Gasserian ganglion of the embryo 



of H inches in length. The sympathetic cord 

 and branches present the same structure. In 

 the ganglia of the cerebro-spinal nerves, the 

 ganglionic corpuscles are larger and more dis- 

 tinctly formed than in the sympathetic ganglia. 

 Many of the cells have processes similar to 

 those above described ; and in several of 

 these, at a short distance from the corpuscle, 

 there is a small oval nucleus such as Kolliker 

 describes in the human embryo of 16 inches. 

 The nerves belonging to the cerebro-spinal 

 system are also much further developed than 

 those in the sympathetic. Those in the bra- 

 chial plexus present the appearance of being 

 composed of a slightly-granular transparent 

 blastema, marked by longitudinal striae, and 

 containing embedded in it oval granular nuclei. 

 The striae are arranged parallel to one ano- 

 ther, and evidently correspond to the margins 

 of the nerve-fibres. The nuclei are arranged 

 at intervals, and occupy the entire breadth of 

 the fibres. There is no trace of the white 

 substance of Schwann. 



Fig. 300. 



From, the semi-lunar ganglion of a Calf 18 inches 

 long. 



a, portion of ganglion ; b, corpuscles isolated ; 

 c, nerve-fibres connected with the ganglion. 



In the sympathetic ganglia of embryos 

 measuring 18 or 19 inches in length, there are 

 still present a considerable number of granular 

 corpuscles measuring from the 4oVo tn to the 

 -y-,1 th of an inch in diameter, similar to those 

 already described. They are chiefly com- 

 posed, however, of cells resembling those in 

 the ganglia after birth, only smaller and more 

 delicate. The nerve-fibres in the ganglia have 

 much the same appearance as those already 

 described in the brachial plexus of embryos 

 from 6 to 8 inches in length. In the ganglia 

 occurring on the posterior roots of the spinal 

 nerves, the Gasserian ganglion, and the gan- 

 glion on the trunk of the pneumo-gastric, the 

 ganglionic corpuscles differ from those in the 

 perfect animal only in point of size. Most of 

 the nerve-fibres connected with the ganglia 

 present the same tubular character as the 

 perfect nerve-fibre. The nerve-fibres in the 

 roots of all the cranial nerves present the dis- 



G G 3 



