GENERAL MORPHOLOGY OE THE CELL 



15 



protoplasm which forms its living basis is a viscid, translucent, 

 granular substance, often forming a network or sponge-like structure 

 extending through the cell-body and showing various structural 

 modifications in different regions and under different physiological 

 states of the cell. Besides the living protoplasm the cell almost 

 invariably contains various lifeless bodies suspended in the meshes 

 of the network ; examples of these are food-granules, pigment-bodies, 

 drops of oil or water, and excretory matters. These bodies play a 

 purely passive part in the activities of the cell, being either reserve 

 food-matters destined to be absorbed and built up into the living 

 substance, or by-products formed from the protoplasm as waste 

 matters, or in order to play some role subsidiary to the actions of 

 the protoplasm itself. The lifeless inclusions in the protoplasm have 

 been collectively designated as nictaplasiu (Hanstein) in contradis- 

 tinction to the Xw-xw-^ protoplasm ; but 

 this convenient term is not in general 

 use. Among the lifeless products of 

 the protoplasm must be reckoned 

 also the cell-wall or vicDibranc by 

 which the cell-body may be sur- 

 rounded ; but it must be remembered 

 that the cell-wall in many cases arises 

 by a direct transformation of the 

 protoplasmic substance, and that it 

 often retains the power of growth by 

 intussusception like living matter. 



In all save a few of the lowest and 

 simplest forms, perhaps even in them, 

 the protoplasmic substance is differ- 

 entiated into two very distinct parts, 

 viz., the cell-body, forming the princi- 

 pal mass of the cell, and a smaller 

 body, the iincleiis, which lies in its 



interior (Fig. 5). Both structurally Fig. 6. — A resting cell {ipermatogo- 



oiArl /^Ko,-.-,;,^oU,r frU^r.^ 4- ^ 4- 1 riiiim) from the testis of the salamander, 



and cnemicaliy these two parts show , • .u . ■ 1 . m, .11 



J 1 li o oi.wvv showing the typical parts. Above, the large 



differences of so marked and constant nucleus, with scattered masses of chro- 



a character that they must be re- "i^^''". .''"i™work and membrane. 



■' Around it, the cyloplasuiic tlircad-work. 



garded as the most important of all Below, the attract'ion-sphere (a) and cen- 



protoplasmic differentiations. The ^'■«^o'»*= W- [After Rawitz.] 

 nuclear substance is therefore often designated as nucleoplasm or 

 karyoplasm ; that of the cell-body as cytoplasm (Strasburger). Some 

 of the foremost authorities, however, among them Oscar Hertwig, re- 

 ject this terminology and use the word "protoplasm " in its historic 

 sense, applying it solely to the cytoplasm or substance of the cell-body. 



