20 THE CELL 



title, " The spongiose structure of protoplasm." Sometimes the 

 description refers to coarser frameworks, which, being due to the 

 deposition in the protoplasm of various kinds of substances, should 

 not be considered as pertaining to protoplasm, nor should they be 

 included in its description. This holds true, for example, of the 

 description of the goblet cells of List (II. 48) (see p. 36, fig. 17). 

 This subject is more fully discussed later on. 



Sometimes net-like structures are described and depicted, which, 

 as they are evidently caused by coagulation (due to some pre- 

 cipitation process), must be considered as artificial products. 

 For instance, artificial framework structures may be easily pro- 

 duced, if a solution of albumen or gelatine be caused to coagulate 

 by the addition of chromic acid, picric acid, or alcohol. Thus 

 Heitzmann (II. 17) demonstrates, in a somewhat diagrammatic 

 manner, the presence of networks in the most various cells of the 

 animal body, which does not correspond to actual fact. Butschli 

 also remarks in his abstract of the literature on the subject 

 (II. 7b, p. 113) : " Above all, it is frequently very difficult to 

 determine whether the net-like appearances described by earlier 

 observers are really delicate protoplasmic structures, or whether 

 they are caused by coarser vacuolisation. Since the same appear- 

 ance is produced in either case, it is only possible to form a fairly 

 correct opinion by considering their relative sizes." Butschli 

 found that in all cases the spaces in the meshes of the protoplasm 

 measured barely 1 fx. 



Thus, although no doubt many statements may be legitimately 

 questioned, yet it is undeniable that many investigators (From- 

 mann, Schmitz, Leydig) have really based their descriptions upon 

 the more delicate structures of the cell. 



In the explanation of these so-called net-work appearances, 

 Butschli takes up a position which is different from that of the 

 other observers who have been mentioned, and which has caused 

 him to advance a foam or honeycomb theory of protoplasm (II. 7a, 

 7b). 



He succeeded in producing a very delicate emulsion by mixing 

 inspissated olive oil with K 2 C0 3 , common salt, or cane-sugar. 



This emulsion consists of a groundwork of oil, containing an 

 exceedingly large number of spaces, which are completely closed in 

 and filled with watery liquid ; if the emulsion is too fine to be seen 

 except under the microscope, the diameter of the spaces is 

 generally less than '001 mm. In appearance they are very like 



