406 SPECIAL HISTOLOGY. 



The structure of the spinal ganglia (Fig. 154) is a difficult subject for 

 investigation, in Man. No complete results can be obtained from the 

 larger of them, but more may be made out in the smaller or smallest, as 

 in those of the fifth sacral nerve and n. coccygeus, which are to be sought 

 within the sac of the dura mater, also perhaps in the fourth sacral and 

 first cervical nerves. If a comparative examination be instituted, of the 

 spinal ganglia- of the smaller Mammalia (Rabbit, Puppy, Mole, Mouse, 

 Rat), and if not only the scalpel and needle be employed, but if the 

 entire ganglia be examined after the application of acetic acid, and above 

 all, of a dilute solution of soda, with the aid of the compressorium, a 

 satisfactory insight into their structure may be obtained. The fibres of 

 the roots of the nerves while passing through the ganglia present nothing 

 at all peculiar, that is to say, no change in size ; nor have I ever 

 observed any divisions of them, and I think it may be positively asserted, 

 that such an occurrence, if it take place at all, must be extremely rare, 

 as, notwithstanding that I have specially sought for it, and have been 

 able, in the lower Mammalia, to trace numerous nerve-fibres through the 

 entire ganglion, I have never noticed anything of the sort. 



The principal constituents of the ganglia — the ganglion-globules or 

 -cells [nerve-cells] (Figs. 155 and 157), have a distinct outer coat, 

 are for the most part roundish, elongated, or pyriform, usually a 

 little flattened,and measure from 0-012 to 0-036, or even 0*04 of a 

 line; on the average 0-02-0 03 of a line. The contents are through- 

 out finely granular, and not unfrequently exhibit, in the vicinity of 

 the nucleus, an accumulation of yellow, or yellowish-brown, larger 

 pigment granules, which increases in age, and to which the gan- 

 glia are chiefly indebted for their yellow color. The nuclei measure 



fasciculi between the perforating nerve-fibres ; in the smaller ganglia they either wind 

 around the nerve-fibres, or rim along the side of the nerve on which the ganglion is situated. 

 This depends mainly on the exact position of the ganglion. If it be placed in the middle of 

 the nerve, the former occurs, whilst if it be situated on one side of it, the latter is the more 

 frequent. 



The new ganglion-fibres mostly proceed peripherally, but according to a recent observer, 

 Axmann (Beitrage zur Anatom. u. Phys. des Gangl. Syst., Berlin, 1853) this is not the case with 

 all of them. From many careful dissections he satisfied himself that whilst, as stated by 

 Kolliker and others, most of the new fibres, proceeding from every spinal ganglion, run in a 

 peripheral direction, and are distributed along with the cerebro-spinal nerve-fibres, to the 

 tissues subjected to will and sensation, some are connected through the rami communic antes 

 with the sympathetic system. He also found that a small number of the ganglion-fibres 

 penetrate through the roots of the cerebro-spinal nerves into the spinal column and brain, 

 where, he states, they have been frequently mistaken for attenuated cerebro-spinal nerve- 

 fibres. He adds, further, that he has been able to trace their connection with the spinal 

 ganglia in the Frog, Mouse, and Pike, and also in a human fcetus of six months. It is, how- 

 ever, difficult to understand how Axmann was able to determine that these fibres proceeded 

 from the ganglia to the spinal marrow, since they might be as readily supposed to have been 

 minute fibres proceeding from the ganglia of the spinal marrow towards the external 

 ganglia. — DaC] 



