118 



Nervous System. 



Tlie two lateral nerves, which, in the strobila lie midway between the 

 ventral canal and the lateral margin, on entering the scolex converge 

 somewhat and pass in well within the rhomb-shaped area enclosed by 

 the suckers. On transverse sections shortly after the cavity of the 

 suckers is reached a rhomboidal commissure is visible, whose angles pro- 

 ject towards the interacetabular spaces and form ganglia there. 



Directly anterior to the rhomboidal commissure, transverse commis- 

 sures connect the four ganglia of the rhomboidal commissure ; these two 

 transverse commissures are fused in the centre and form a cross. 



Prom each of the four gangha in the angles of the rhomboidal com- 

 missure four nerves originate, one laterally going to each of the two 

 adjacent suckers, the other two ascending, at first towards the summit 

 of the scolex. then bending over and forming loops with each other, the 

 right ventral fusing with the right lower (ventral) lateral, the upper (dorsal) 

 right lateral with the right dorsal, the left dorsal with the upper left 

 lateral, and the lower lateral with the left ventral. 



A large median plate, poor in ganglion cells, appears to lie further 

 anteriorly, just below the anterior loops of the lateral canals, but I have 

 not been able to trace the connection of the plate with any of the eight 

 nerves (four loops). 



The lateral nerves on transverse sections fixed with silver nitrate 

 appear to consist of a dark network, containing many small black granu- 

 lations (precipitate of silver 1) on the meshes. The meshes become rather 

 denser towards the margins. There is no membrane between the nerve 

 and the parenchyma. Small cells, glia cells, are frequent, especially on 

 the circumference of the nerve; some are, however, situated in the depth. 

 These glia cells are very poor in protoplasm, only their vesicular nuclei 

 with a large nucleolus being visible. The nucleus measures about 4-5 /" 

 by 3 ^. Where the nerve is not cut transversely, but obliquely or longi- 

 tudinally, the network is seen to consist of more or less parallel fibres. 

 Large ganghon cells are very frequent in the rhomboidal and transverse 

 commissures and in the nerves originating there, and also in the body 

 of the suckers. (Fig. 3.) 



The ganghonic cells in the nerves are elongate, fusiform, and in some 

 cases appear to be bipolar. 



Their long axis always hes parallel to the axis of the nerve. These 

 cells vary in size, their apparent total length in a section, of course, 

 depending on the angle in which the plane of the section has cut them. 



The processes originating from these cells can often be traced for a 

 long distance in the nerve. The protoplasm of these nerve-cells is almost 

 invariably filled with short rod-shaped bodies, arranged serially, each 

 series more or less parallel to the next, staining dark blue with haema- 

 toxyhn (tigroid bodies). ^These structures also occur for some distance 

 along the nerve processes. The nucleus is oval, vesicular, staining very 



