THE STRUCTURAL BASIS OF THE BODY 



19 



FIG. 5. Diagram of a cell 

 highly magnified. (SCHAFER.) 

 p, protoplasm, consisting of 

 hyaloplasm and a network of 

 spongioplasm, ex, exoplasm ; 

 end, endoplasm, with distinct 

 granules and vacuole s; 

 c, double centrosome ; n, nu- 

 cleus ; n', nucleolus. 



plasm between them will be converted into alveolar partitions between the 

 droplets. In many an egg cell, where there is a growth of protoplasm from 

 this building up of food into reserve materials, the development of such 



an alveolar structure can be followed in the 

 living protoplasm, and such cells when mature 

 show a marked alveolar structure whether ex- 

 amined fresh or in the hardened and stained 

 condition. Such a protoplasm would be prac- 

 tically an emulsion of one fluid in another, and 

 according to Butschli, artificial emulsions, made 

 by mixing rancid oil with sodium carbonate 

 solutions, may show under the microscope a 

 very close resemblance to cell protoplasm 

 (Fig. 6), and may even exhibit amoeboid 

 changes of form in consequence of the diffusion 

 currents set up at the surface of the drop 

 between its contents and the surrounding 

 water. Most histologists are in accord that 

 none of the above theories can be regarded as applicable to all forms of 

 protoplasm,but that during the life of a cell its protoplasm, as observed 

 under the microscope, may be either 

 hyaline and structureless or may 

 present any of the structural modi- 

 fications described above, according 

 to its state of nutrition and the form 

 in which its metabolic products are 

 laid down in the cell. Of course 

 it is possible that, even in the 

 apparently hyaline protoplasm, a 

 structural differentiation is still pre- 

 sent, but is invisible owing to the 

 minute size of its constituent parts 

 or an identity of refractive index 

 between the alveolar walls and their 

 contents. The fact that; every 

 chemical differentiation occurring 

 within the colloidal mass will tend 

 to cause differences of surface ten- 

 sion, and therefore . formation of 

 droplets, shows that an alveolar 

 structure, i.e. one in which there is 

 a large number of surfaces separat- 

 ing heterogeneous mixtures inside 

 the cells, must be of very common 

 occurrence, even in cases where it is not detectable under the microscope. 

 Such a structure must be present, at any rate, in those cases where, apart 



FIG. 6. A, protoplasm of an epidermal cell of 

 the crayfish ; B, foam-like appearance of 

 an emulsion of olive oil. (BUTSCHLI.) 



