l82 FINE-STRUCTURE OF PROTOPLASM II 



an invisible fine-structure, detailing of which falls within the province 

 of submicroscopic morphology. A further task is to establish the 

 nature of the plasma liquor (enchylema, paraplasm, matrix). 



Very many of the hypotheses relating to the structure of cytoplasm, 

 discussed in former times (Lundegardh, 1922, p. 242), are irre- 

 concilable with our own views. Nowadays the emulsion and alveolar 

 theories can no longer be regarded as valid. Taking clotted milk as 

 an example, Seifriz (1936) shows how the droplet theory takes ac- 

 count only of the relatively coarse units, whereas the fine-structure is 

 caused by the fibre structure of the casein. He applies this model to 

 cytoplasm and is thus led to a scheme of protoplasmic structure which 

 tallies well with ours, so long as we bear in mind that, when living, it 

 does not represent a fixed coagulum of protein particles, because the 

 particles may be reversibly released and move freely and independently 

 of each other. Further comparison of the proteins of protoplasm with 

 a heap of rodlets seems less felicitous to me, since such a heap has 

 a fortuitous, statistical character, whereas the structure of protoplasm 

 must be a co-ordinated whole. Its framework cannot be a disorderly 

 pile; it must surely consist of an organized and well-defined structure. 



According to our present knowledge, all hypotheses of proto- 

 plasmic structure which postulate permanently individualized sub- 

 microscopic particles (granules, droplets, alveoles, ultramicrons) must 

 be discarded as being corpuscular theories. The framework structure of 

 gelated cytoplasm possesses no dispersed phase in the sense of the 

 classical theory of colloids: both the framework and the enchylema 

 are continous throughout the whole space available. For the same 

 reason Butschli's foam structure or honeycomb theory cannot be taken 

 into account, in spite of its numerous merits, for a honeycomb con- 

 sists of closed dispersed regions in contradistinction to the open and 

 continuous system of interconnected strands. 



Flemming's fibrillar theory, on the contrary, conforms rather well 

 with the condition of a complete intermeshing of strands and dis- 

 persing medium shown to be likely in this monograph. Here again, 

 however, the fibrillar structure has to be transferred to submicro- 

 scopic regions. In fact, in a three-dimensional network, both the 

 contours of the meshes and the meshes themselves fill all space 

 continuously. Monne (1946 a) is of the opinion that the protoplasmic 

 fibrils do not form a network, but are only plaited (in German: Flecht- 



