49 



The external irorpholoi^y of a neurone from the middle re- 

 gion of the nucleus is shown in Pi^^.^. Such a neurone is con- 

 siderably larger in size than any neurone from the substantia 

 gelatinosa. Prom an elongated-oval or triangular cell-body, 

 three or four dendrites proceed straight outward into the tan- 

 gle of nerve-fibres and neuroglia. A dendrite is a rather 

 stout process. It has but few branches, and these are of small 

 size. Its surface bears scattering gemmules and minute knobs. 



The axone takes its origin directly from the cell-body. 

 It runs in a medio-ventral direction. 



Two neurones stained with methylen-tlue are represented 

 in Pig.4S. These are from the median collection just dorsal 

 to the lotus vagi. The nucleus of such a neurone is propor- 

 tionately quite large. It is also eccentric in its position, 

 consequently cells are often found in which the nucleus appears 

 to be in direct contact with the cytoplasmic pellicula at some 

 point. The nucleoli are of some prominence. The chromatic 

 material is also conspicuous. It is distributed in branching 

 strands of some thickness in places, and the several strands 

 may have slight connections. 



The cytoplasm is often practically absent at the side of 

 the nucleus. The dendrites are so thick, relatively, at their 

 bases that the greater part of the cytoplasm appears collected 

 in them. The tigroid substance is most abundant in the vicin- 

 ity of the nucleus. The individual masses here are usually 

 irregular in form and quits small in size. In the basal parts 



