VII INTRA- CELLULAR NERVE-FIBRILS 351 



In the latter the cilia are connected at their bases with fine 

 fibrils, which probably pass through the nucleus and form the 

 continuation of nerve-fibrils. 



Lastly, it is evident that the nerve-fibrils start from the 

 nucleoli of the nerve-cells, for they pass in a radiate manner 

 from the nucleolus and form a fibrillar network in the 

 nucleus. On the other hand, the same histological relations 

 are seen in nuclei in which nerve -fibres terminate, most 

 clearly in Medusse, but also in the higher animals. I con- 

 sider the so-called " Elmer's ring of granules," which is also 

 most clearly to be seen in many nerve-cells, to indicate the 

 points where the fibrils radiating from the nucleolus bend 

 round to join the complicated network of the nucleus.^ 



This fibrillar network in the nucleus — and this is the par- 

 ticular bearing of the preceding upon our subject — must, 

 like the fibrils in the cell which are connected with it, be of 

 nervous nature, and this is undoubtedly the condition of 

 things in the ganglion-cells of the higher animals : it can be 

 seen, for instance, in the cerebral ganglia of the Helix 

 pomatia. Even in Medusie (in the marginal bodies) definite 

 fibres of extraordinary delicacy serving exclusively as nerves 

 liave arisen ^ — the " dotted substance " in the brain of hii^her 

 animals is the indication of a fibrillar network connectino- 

 the cells, and the structure of this is so delicate that it will 

 probably never be possible to follow out the course of the 

 fibrils. But these nerve-fibrils must have been derived from 

 simple strands of ordinary protoplasm, and such they are still 

 in cells which are not specifically nervous. 



From such protoplasmic strands true nervous substance 

 with infinitely delicate and regular connections must have 

 been formed by the constant passage of nervous impulses and 



1 Cf. Die Medusen, Taf. viii. fig. 6, 7 ; Taf. ix. figs. lOn ; Taf. xi. fig. 10 ; 

 Be7'oe, Taf. viii. bes. fig. 82 ; and Weitere Nachrichten iiber den Bait, des Zell- 

 kernes, etc., loc. cit. Taf. vii. 



- Cf. Die Medusen, Taf. iv. figs. 2, 6, 13, 1 i, etc. 



