246 



NERVOUS SYSTEM. 



[SECT. 120. 



Fig. 102. 



with the axis cylirder. In older ganglionic globules, or after the action of 

 re-agents (arasixous acid, chromic acid, iodine), the contents of cells, as was 

 first demonstrated by BTarting, separate from the membrane, and the axis 



cylinder appears as a direct continua- 

 tion of them (fig. 102). The ganglionic 

 fibres, frequently surrounding the cells 

 in an arched form or in several coils, 

 are, at first fine, of o'ooi 5'" to o - oo25'" in 

 diameter. They do not, however, remain 

 so, but, as may in many cases be very 

 readily observed directly, increase very 

 soon in thickness, so that even within 

 the ganglion, all measure 0-003'" an< i 

 o'oo^'", many v even o , oo5"' and o - oo6'", 

 and have, consequently become medium. 

 thick, and thick nerve-tubes. The pro- 

 cesses of the cells and the nerve- fibres 

 arising from them possess, like the 

 cells themselves, nucleated sheaths, the 

 so-called sheath processes ; they lose 

 them, however, at the point where they 

 enter the trunk passing out of the 

 ganglion, and then receive the ordi- 

 nary neurilemma of the nerves as a 

 covering. 



The account I have just given of the 

 relation of the spinal ganglia of man 

 and mammalia, deviates very consider- 

 ably from what Bidder, Reichert, R. 

 Wagner .and Robin, in 1847, found to 

 be the case in -fish. The main differ- 

 ence consists in this, that whilst in 

 mammalia, as far as we know, the roots 

 enter into no direct relation to the ganglionic cells, and sinrply pass through 

 the ganglia, in fishes all the nerve-fibres are connected with them, each fibre 

 being interrupted by a bipolar cell, without any special ganglionic fibres 

 at all. 



,7 



Ganglion globule from the pike (so called 

 bipolar), running out at both ends into dark- 

 bordered nerve-tubes, treated with arsenious 

 acid, and magnified 350 times, a. Envelope 

 of the globule. 6. Nerve-sheath, c. nerve- 

 medulla, d. The nerve-fibre connected with 

 the contents (e) of the ganglion-globule which 

 are retracted from the envelope. 



§ 120. Further Course and Termination of the Spinal Nerves. — 

 Beyond the spinal ganglion, the sensitive and motor roots join to 

 form a common trunk, by intermixture of their fibres, as can be 

 very distinctly observed in small animals. All subsequent off-sets 

 from the anterior and posterior main branch, as well as from their 

 further ramifications, are, consequently, of a mixed nature, and 

 formed of fibres from both roots; this condition is maintained even 

 to their last ramifications. Here, however, this relation becomes 

 altered, the motor fibres going, in by far the greater majority, into 

 the muscular twigs, and the sensitive into the cutaneous branches. 



