24 



GENERAL PHYSIOLOGY 



Butschli,^ in fact, believes that it possesses a honeycomb or froth-like 

 structure. These somewhat divergent views may be classified under 

 the following heads : 



(a) The granula theory, proposed by Altman,^ holds that the 

 granules contained in protoplasm are the essential constituent and that 

 the fluid medium is not living substance at all. 



(6) The fibrillar theory assumes that the protoplasm consists of a 

 network or clusters of fibrils containing in its meshes a certain amount 

 of fluid material. The fibrillar reticulum or sponge work is designated 



by Schafer as the spongioplasm and the 

 more fluid and structureless portion as the 

 hyaloplasm. 



(c) The alveolar theory, advocated by 

 Btitschli, contendg that the ground-substance 

 of the cytoplasm stores its material as 

 globules which gradually increase in size 

 and become separated from one another 

 by alveolar partitions. Microscopic for- 

 mations of this kind may be produced artifi- 

 cially by mixing oil with potassium or cane 

 sugar. On bringing a droplet of this oil in 

 contact with water, molecules of the latter 

 pass inward and spHt the oil droplet into 

 innumerable smaller ones until a very deU- 

 cate froth is produced. The diffusion cur- 

 rents resulting in this mixture, are at times 

 so intense that movements similar to ame- 

 boid motion may be observed. 



The nucleus of the cell appears as a rule 

 as an oval or round body, situated near the center of the cytoplasm 

 and sharply differentiated from it by what is known as a nuclear 

 membrane. Many cells, however, contain nuclei which are long 

 drawn out or constricted so as to form band-like or bead-like chains 

 of nuclear material, while in others the nuclear material is scattered 

 through the cytoplasm in the form of dust-like particles. Consider- 

 able variations are also noted with regard to the relative volume of 

 the nucleus and cytoplasm, the latter forming at times merely a narrow 

 frame around a large centrally placed nucleus. 



The nucleus consists of an enveloping membrane, a network of 

 fibers, the nuclear matrix and nucleoh. It is beUeved that the spongio- 

 plasm of the cytoplasm is extended into the nucleoplasm, but on a 

 larger scale, i.e., the threads are coarser and can therefore be more 

 easily seen. The interstices of this network are filled with nuclear 

 sap or matrix. At the different points of crossing, of the filaments, the 



^ Untersuchungen iiber die mikrosk. Schaume und das Protoplasma, Leipzig, 

 1892. 



2 Die Elementarorg. und ihre Beziehungen zu den Zellen, Leipzig, 1890. 



Fig. 1. — The Structure of 



Protoplasm. 

 An epidermal cell of the earth- 

 worm. (After Biltschli.) 



