454 



SPECIAL HISTOLOGY. 



Fig. 157. 



of which occurs everywhere, and the latter principally in the 

 larger ganglia, certain intermediate types are met with in 

 Man, which consist, as it were, of nucleated ' fibres of Remak/ 

 as they are termed (vid. infra), or, at all events, in the pre- 

 paration, break up into such. 



From by far the greatest number of the nerve-cells, in Man 

 and the Mammalia, are given off pale processes, 0"0015 — 

 00025'", in all respects corresponding to those of the central 

 cells, but furnished with a special sheath, and which, as I dis- 

 covered in the year 1844 ( c Selbst. u. Abh. des Symp. Nerv./ 

 Zurich, 1844, p. 22), are each of them continued into a dark- 

 bordered nerve-tube (figs. 155, 157). The cells observed by 



me had but one pro- 

 cess, the so-termed 

 unipolar-cells, and I 

 at first thought that 

 such onlv existed in 

 the spinal ganglia. 

 It now appears, how- 

 ever, from more re- 

 cent researches, es- 

 pecially from those 

 of Stannius, that they also contain cells with two processes, 

 one of which may agaiu divide ; fresh and more extended 

 investigations therefore are required to show how the matter 

 really stands. At present I think the following should be 

 remarked : 1. in Man and the Mammalia I have certainly 

 established the fact of the existence of unipolar-cells, and 

 think it may also be asserted that they are very numerous; 

 2. quite lately I have myself, although rarely, noticed cells 

 with two, pale processes, and I am willing to admit the pos- 

 sibility that such cells frequently occur, as it is certain that 

 many processes must be torn off in the comparatively rude 

 methods necessarily employed to isolate the cells ; 3. when 

 Stannius very recently noticed in a human foetus, and in a 

 foetal Calf, together with unipolar and apolar cells, in the 

 latter numerous bipolar cells, it should be inquired whether 



Fig. 157. Tsvigs of the coccygeal nerve within the dura mater, with an adherent, 

 pedunculated nerve-cell in its nucleated sheath, from which the derivation of a fihre 

 is very distinctly seen, x 350 diam. From Man. 



