CYTOPLASMIC INCLUSIONS 177 



ble to distinguish between permanent organelles and temporary com- 

 ponents, nor between active and passive granules. 



The Classification of Cytoplasmic Granules 



The cytoplasmic granules are a visible reaction of the cell to various 

 stimuli, with the result that they show as great a variety as do the func- 

 tions of which they are the visible expression and as the cells which form 

 these granules. Any final classification must be based, then, on function, 

 composition, and origin, rather than on a few nonspecific stains which 

 give the impression of universal components, or on a distinction between 

 permanent organelles and temporary reserves. Since function, composi- 

 tion, and relationship vary widely from one cell to another, the cyto- 

 plasmic granules, even of the Protozoa alone, cannot be divided into 

 three or four sharply defined types, but must be separated into more 

 types, with a classification sufficiently flexible to allow for the combina- 

 tion of several functions in the same granule. Such an ideal classification 

 may be defined briefly as functional. 



A functional classification is impossible at the present time, since the 

 usual cytological or cytochemical methods reveal only those functions 

 which result in the accumulation of visible masses of material — the 

 segregating functions. The general type of material which is segregated 

 has been identified in many cases, but usually there is insufficient evidence 

 to determine whether this is a simple segregation process or whether 

 there is actual synthesis involved. A functional classification on such a 

 narrow base would lack permanent value, but it is necessary to readjust 

 the present classification, in order to separate granules which are obvi- 

 ously unlike, even on the relatively scanty evidence now available. This 

 separation has been outlined in the previous sections with the detailed 

 evidence, but it is worthwhile to assemble these suggested changes here 

 in one place. 



The mitochondria are those granules which respond to mitochondrial 

 methods, such as those employed by Regaud, Benda, and so forth, and 

 which usually segregate Janus green. This is admittedly a heterogeneous 

 group, but there is insufficient information at present to separate any 

 groups on a logical basis. 



The term Golgi body is used to designate granules or structures which 

 impregnate specifically with the classic reduction methods, but excepts 



