

THE CELL. 



23 



and possesses a thick, porous, nuclear membrane. It is very similar 

 to the multinucleated germinal vesicle of the ovum of an amphibian. 

 Simultaneously with the advent of the ceiitrosome into the proto- 

 plasm, there appeared in the latter, which heretofore has been entirely 

 free and clear, a large number of very small nuclei. These act as 

 centers, around each one of which there develop nucleated zoospores, 

 which may amount finally to as many as some hundreds of thousands 

 of separate cells. 



B 



Fig. 4. To Show the Changes in the Nerve-cell Due to Age. 

 (From HOWELL.) 



A, Spinal ganglion cell of a still-born child. B, Spinal ganglion cell of a 

 man dying at 92 years of age. N, Nuclei. In the old man the cells are not 

 large, cytoplasm is pigmented, the nucleus is small and the nucleolus much 

 shrunken or absent. Both sections taken from the cervical ganglion. 250 

 diameters. (HODGE.) 



Fatigue of Cells. Hodge, of Clark University, has found 

 changes in the cell corresponding to rest or activity. Thus the nerve- 

 cell in the morning has a clear, round nucleus, while in the evening, 

 being tired from work, the nucleus has an irregular contour. 



LITERATURE CONSULTED. 



Verworn, "General Physiology," 1899. 

 Hertwig, "The Cell," 1895. 



