2 The Microscope. 



The single cell of the Amoeba constitutes the entire individual, 

 leading an independent existence, and ministering only to its 

 individual needs; the colorless blood corpuscle, on the contrary, 

 is but one of a great community of cells, each member of which, 

 while primarily concerned in its own necessities, is engaged in 

 the maintenance and promotion of the general wealth of the 

 entire organism. 



The structure of the protoplasm of these elements is a sub- 

 ject which has attracted much attention and elicited bitter dis- 

 cussion. As usual, the truth lies midway between the extremes 

 of the conflicting opinions. It is now well established, and 

 generally accepted, that the living protoplasm of active cells, as 

 the colorless blood corpuscles, is composed of two parts : the 

 active, contractile, albuminous bioplasm, and the relatively 

 inert paraplasm ; upon the arrangement of these two constituents 

 of the cell does the appearance of its proto]>lasm depend. Where 

 both bioplasm and paraplasm occur as closely intermingled par- 

 ticles a finely granular appearance results; where the protoplasm 

 is heaped up together, dividing the protoplasm into bands and 

 septa, a more or less perfect network or reticulum is formed. An 

 important fact to be appreciated in this connection is, that the 

 arrangement of the constituents of protoplasm is not constant, 

 but subject to continual change, a truth that every one who has 

 carefully studied the white blood cell under high powers must 

 admit; in such elements, the formation, transient piesence, and 

 disappearance of networks are continually occurring, demon- 

 strating the inaccuracy cf describing temporary conditions as 

 the constant structure of protoplasm. In cells more highly 

 specialized than the colorless blood corpuscle, especially in those 

 where particles of secretion are often stored, as in the glandular 

 epithelium, a reticulated condition of the protoplasm is very 

 marked ; the bioplasm is pushed aside by the inert substances, 

 the entire cell assuming a sponge-like arrangement, in which the 

 framework is formed by the active contractile substance, while 

 the passive materials fill the interspaces. 



The reproduction of the white blood cell is of interest, as 

 affording one of the gradually decreasing group for which the 

 direct mode of division is still recognized. That division in the 

 simplest manner does here take place seems to admit of little 

 doubt, but, on the other hand, it is highly probable that the in- 



