No. 2.] CHANGES IN NERVE CELLS. 107 



lated in some cases, in others not ; was broken up into lumps 

 and granules which had lost fibrillar structure in part or alto- 

 gether, and showed waxy degeneration. Some fibres exhibited 

 the discoidal breaking up of muscle substance commonly seen 

 in typhoid fever. That is, the mechanism was broken, not 

 exhausted. The muscle nuclei showed no* change whatever. 

 Possibly the vacuolation which appears in some instances may 

 be reckoned as genuine fatigue effect. 



Under this head I may call attention to a few points in the 

 metabolism of another mesoblastic tissue ; viz. the blood. 



Alice Leonard (41, p. 39) points out the fact that the blood is 

 greater in amount in November than at any other season, and 

 the red corpuscles stain bright red with eosin at this time. 

 During the winter they take the stain less and less, become 

 smaller, until the minimum is reached in May. By July they 

 begin to enlarge again and to take the stain. The nuclei, more- 

 over, stain differently at different seasons and are found to dif- 

 fer both in structure and form, staining in some corpuscles 

 densely, in others showing the usual reticulum. They may also 

 appear shrunken and irregular or oval and clear. 



Something similar for mammalian corpuscles while still nu- 

 cleated is pointed out by Howell (26). Immature erythroblasts 

 are nucleated red corpuscles having a large reticulate nucleus and 

 a small amount of haemoglobin. These divide by karyokinesis for 

 several generations until finally a form is reached, the mature 

 erythroblast, having a smaller densely stained nucleus and large 

 amount of haemoglobin. When the nucleus has lost its reticu- 

 lum, no further division is possible, and it is then extruded from 

 the corpuscle to be dissolved in the plasma. 



Nerve Tissue. 



All nerve cells are phylogenetically cells of the epiblast. In 

 any section of skin, from the deepest layer of columnar cells to 

 the horny scales at the surface, we may observe a series of 

 changes which have a deep physiological significance. Here we 

 have at a glance the life history of an epithelial cell. Is it the 

 story of a cell being born, growing to maturity, and dying of old 

 age .'' It may be so. Or is it the case of a cell being crowded 

 away from its supply of nourishment and dying of starvation .'' 



