STRUCTURE OF CELL-PROTOPLASM. 



173 



of protoplasm is applied is a completely homogeneous material, which, although it 

 might contain granules of solid matter or globules of watery fluid (vacuoles) im- 

 bedded in it, is nevertheless itself entirely devoid of structure (fig. 201, A). It is 

 possible that this view may still hold good for some cells both animal and vegetable, 

 but in most cells, especially those which are " fixed " or non-amoeboid, it is found that a 

 differentiation of the protoplasm has occurred in such a manner that a part of it 

 appears under high powers of the microscope in the form of a network or spongework, 



__ -p. 



Fig. '201. A, DIAGRAM OF A CELL, THE PROTOPLASM OF WHICH APPEARS STRUCTURELESS, BUT is OCCUPIED 



BY VACUOLES AND GRANULES. B, DIAGRAM OF A CELL, THE PROTOPLASM OF WHICH IS COMPOSED OF 

 SPONGIOPLASM AND HYALOPLASM. 



p, protoplasm ; n, nucleus; ', nucleolus. 



Fig. 202. CELL FROM THE EPIDERMIS OF AN EMBRYO OF SALAMANDRA, TREATED WITH 1 PER CENT. 

 HYDROCHLORIC ACID. (After Kolliker.) 



7i, nucleus, with network of chromoplasm ; p, protoplasm, showing a reticulum of plastin. 



whilst the rest of the protoplasm occupies the meshes of this network (figs. 201, B, and 

 202). The network is known as the reticulum or spongioplasm ; while the substance 

 which occupies its meshes may be designated the enchylema (Carnoy) or hyaloplasm. 



Fig. 203. CELL WITH RADIALLY DISPOSED 



RETICULUM FROM THE INTESTINAL EPI- 

 THELIUM OF A WORM. (Carnoy.) 



me, membrane of the cell ; pc, pro- 

 toplasm of the cell ; mn, membrane of 

 the nucleus ; pn, achromatic substance 

 of the nucleus, with the convoluted chro- 

 inatin filament, bn, contracted into the 

 centre. 



me 



pc- 



The proportion which these bear 

 to one another varies in different 

 cells, but it may be stated that as 

 a general rule the amount of 

 spongioplasm becomes augmented 

 as the development of the cell 

 proceeds, and that the younger a 

 cell the greater is the relative 

 amount of hyaloplasm. 



The shape and size of the meshes of the reticulum also vary in different cells, 

 and even in different parts of the protoplasm of the same cell. Thus in some cells 

 the constituent fibrils or cords of the spongioplasm are disposed radially from the nu- 

 cleus to the periphery (fig. 203), and the meshes are radially elongated ; in others they 

 are disposed evenly in all directions, whilst in some a concentric disposition of the 

 fibrils can be determined. The fibrils are invariably united together (as is implied by 

 the use of the term reticulum) into a network, and at the nodes of the network where 



N 2 



