GANGLION CELLS NANS EN'S VIEWS 147 



have found no evidence of any kind in support, and regard this 

 opinion as incorrect. Nansen thinks that the protoplasm of 

 the ganglion cells is composed of two different kinds of con- 

 stituent elements first, of the reticulate so-called spongioplasma, 

 which extends from the fibrous neuroglia sheath into the 

 ganglion cell ; and secondly, of the true nerve tubules, which, 

 as has been stated, penetrate through the processes into 

 the ganglion cell, and emerge again in the same manner. Every 

 such primitive nerve tubule is supposed to be enveloped in a 

 delicate sheath of spongioplasma, which is in direct connection 

 with the reticulate spongioplasma of the ganglion cell. As has 

 been said, I consider this view, viz. that the ganglion cell is 

 built up of two different elements a view which, if correct, 

 would separate this structure from the typical cell series as 

 in no way warranted. Nansen's view is supported chiefly 

 on the relations of the ganglion cells observed in Homarus and 

 some other animals. Here bundles of such nerve tubules are 

 said to be found cut through in sections at the periphery of the 

 cell or even scattered through its whole body, which are dis- 

 tinguished from the spongioplasmic ground substance by their 

 lighter appearance, and are proved to be transverse sections 

 of bundles of such nerve tubules by their distinct reticular 

 structure, resembling the peripheral nerve fibres, which are in 

 like manner interpreted as bundles of the same kind. 



Now it seems to me beyond a doubt that Nansen is deceived 

 with regard to this supposed bundle of nerve tubules, and 

 that they were nothing more than larger vacuoles, which not at 

 all infrequently make their appearance in the protoplasm of 

 ganglion cells. In the cells of the ventral nerve cord of 

 Lumbricus I have frequently observed a large number of such 

 vacuoles, and other observers also, e.g. Rohde (1887), have found 

 them commonly in Polychaetes, especially in the periphery of the 

 cell. Rohde believes they should be regarded as collections of 

 the ground substance, termed paramitome, of the protoplasm. In 

 Lumbricus Nansen also has frequently seen these vacuoles, but is 

 inclined to explain them as cross sections of nerve tubules. 

 The correctness of my interpretation of these supposed bundles 

 obtains still further support from the fact that Nansen himself 

 has frequently pointed out their resemblance to vacuoles. The 

 apparent reticulation of these vacuoles is well explained from 

 the fact that if not focussed very sharply, at one time the 

 reticulate meshwork of their floor, at another that of their roof, 

 comes into view, giving the erroneous idea of reticulated contents. 

 If it was really a matter of bundles of nerve tubules which 

 passed through the so-called spongioplasma, they ought then to 



