THE CELL. 9 



Its refractive power is greater than that of water and in it, as 

 a medium, very delicate threading of protoplasm may be distin- 

 guished. It was formerly supposed to be composed of a homogeneous 

 material, and destitute of any structure and to contain a number of 

 minute granules of a solid nature. 



Under the high powers of the microscope, when properly stained 

 with reagents, it has been found that the protoplasm consists of two 

 parts: (1) a fine network of fibers, like a sponge, called the reti- 

 culum, or spongio plasm ; and (2) the more fluid portion in the 

 meshes, called the enchylema, or hyaloplasm. However, it must be 



Fig. 3. Amoeba Proteus. (LEIDY.) 



n, Nucleus, cv, Contractile vacuole. N, Food-vacuoles. en, Endoplasm. 

 ek, Ectoplasm. 



mentioned that the views concerning the structure of protoplasm dif- 

 fer, several theories being offered. According to the first idea, the 

 protoplasm forms the network, the nodal points of which appear as 

 individual granules. It is very probable that many of the larger and 

 more obvious granules are inert bodies, such as glycogen, mucin, 

 fat-globules, albuminous substances, etc., suspended in the network. 

 The glycogen granules are found in the liver-cells, the fat-globules 

 in the cells of the lacteal glands, and the pigment-granules in the 

 skin-cells of many colored animals. Sometimes, in unicellular ani- 

 mals, calcareous matters are found, although those most uniformly 

 found are of the same general nature as the protoplasm. All these 

 particles, or granules, are termed microsomes. Besides, there are 



