



lillimeters 



0.5 



Figure 256. — Visceral ganglion of C. virginica. Transverse section at the right angle to the fibers of the adductor 



muscle. Bouin, hemato.xylin-eosin. 



(1912) pointed out that the interstitial elements of 

 the nenropile do not isolate the nervous elements, 

 while in the nerves and in the commissures the 

 glia cells surround a number of nerve fibrillae 

 which form distinct tracts. Of the three different 

 types of glia cells described by Jakubski, the 

 narrow, spindle-shaped cells could be seen in the 

 preparation of the ganglia of f\ inrginica stained 

 with Delafield and iron hematoxj'lin. Nissl 

 granules were described in tlie multi-polar nerve 

 cells at the ends of siphons in Mya (Pieron, 1941). 

 The nerve fibers which form the neuropile are 

 clearly noticeable in sections of the visceral gang- 



lion (fig. 256) ; some of them cross the ganglion, 

 while others enter the viscero-cerebral connective 

 on the same side where they emerged. 



Rawitz (1887) described in detail the pathways 

 of these fibers in the visceral ganglion of Mytilus. 

 He found that in each half of the ganglion approx- 

 imately one-quarter of the fibers originates from 

 the nerve cells of the same section; one-quarter 

 arises from the opposite half; one-quarter is 

 derived from the cerebro-visceral connective of the 

 corresponding side; and one-quarter originates in 

 the cerebro-visceral connective of the opposite side. 

 It is difficult to determine these pathways in the 



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