MODIFICATION IN THE FOKM OF CELLS. 



27 



the original cell in size and in as 

 vet unmarked individual char- 

 acteristics which in the speciali- 

 zation of function of the organ- 

 ism will cause them finally, for 

 the : most part, to lose all mor- 

 phological resemblance to the 

 parent cell. 



These differences in cells 

 produced in the development of 

 the organism are very numer- 

 ous. 



First, as regards their size, 

 we find cells varying from the red 

 blood-cell -g-g 1 ^ to the large 

 ganglion-cell, ^<y of an inch 

 (Figs. 18 and 19). 



In nearly all instances where 

 a collection of cells develop into 

 an organ or tissue the original 

 spherical form is lost, often 

 merely from mutual pressure and 

 from alteration in the cell-con- 

 tents, by which the most varied 

 forms are produced. Thus, 

 instead of the spherical form, 

 cells may take on an oval, elon- 

 gated shape (Fig. 20), or may be 

 cylindrical (Fig. 21), or again 

 from mutual pressure may form 

 regular hexagons. Others may 

 have long, thread-like attach- 

 ments developed, as in the sperm- 

 cells (Fig. 22), or even a number 

 of such prolongations, which as 

 long as the cell is alive continue 

 in active movement (ciliated 

 cells). (See Fig. '21.) 



Often the nucleus deviates 

 from its spherical form, and may 

 become oval or, irregular in out- 

 line,, or, as in certain cells of 

 the marrow of bone and in 



FIG. 18. RED AND WHITE BLOOD-CORPUSCLES, 

 ENLARGED Six HUNDRED DIAMETERS. 



(Ellenberger.) 



A, surface view of red corpuscles ; B, profile view ; C, rou- 

 leaux of red corpuscles ; D, central depression in red corpuscles : 

 E, crenated red corpuscles ; F, small, and G, large white cor- 

 puscles. 



FIG. 19. AN ISOLATED GANGLION-CELL OF 

 THE ANTERIOR HORN OF THE HUMAN 

 SPINAL CORD, AFTER GERLACH. (Klein.) 



A, axis-cylinder ; B, pigment. The branched processes of 

 the ganglion-cell break up into the fine nerve net-work shown 

 in the upper part of the figure. 



