470 



OF GENERAL PHYSIOLOGY 



elements in the cytoplasm : (1) Large granules or masses which stain deeply with 

 "basic" dyes, and are called, from their discoverer, "Nissl Bodies," and (2) an 

 appearance of fine fibrils passing through the cell substance from one process to 

 another, "neuro-fibrils." Now Mott (1912) and Marinesco (1912) have made 

 very careful examinations of living nerve cells, partly by the aid of the ultra- 



a 



FIG. 144. 



LIVING NERVE CELLS FROM THE DORSAL ROOT GANGLIA, AS SEEN 

 WITH THE ULTRA-MICROSCOPE. 



a, Normal cell, from dog three days old. Fine colloidal particles in cytoplasm, showing Brown jan 



movement. Nucleus appears nearly empty. No indication of Nissl bodies, nor of neuro-fibrils. 

 No amoeboid movement of the cell as a whole was noticed. 



b, Similar cell from new-born dog. More highly magnified. Collection of particles around nucleus. 



c, From ganglion in lumbar region of new-born dog. Large, brilliant granules are seen where the 



axone leaves. 

 **, Five cells from small dog. They showed spontaneous changes under observation. The brighter 



areas, due to larger particles, changed their positions in the cells. 

 e, Two cells, which had been treated with sodium iodide for eight hours. Appearance of larger 



aggregates of particles, surrounded by smaller ones still showing Brownian movement. 



(Marinesco.) 



microscopic method of brilliant dark-ground illumination (see page 82), and agree 

 in the statement that neither Nissl bodies nor neuro-fibrils are present in the 

 living state ; a result which might be suspected from the work of Hardy described 

 in Chapter I. of this book (see Fig. 144). The considerations of that chapter as to 

 cell protoplasm in general apply to that of the neurone. It is seen to be full of fine 

 granules, behaves as a viscous fluid, and, to reagents, responds as an electro- 

 negative colloid. Without denying the value of observations on fixed cells, Mott 





