1 CYTOPLASM l8l 



that morphogenetic manifestations of the cytoplasm are only possible 

 in its gelated state, for this alone permits it to assume shapes different 

 from those induced by the surface laws of liquids. Submicroscopic 

 morphology is therefore very much concerned to know the type of 

 junctions by which the macromolecules of the cytoplasm lose their 

 individuality and aggregate to form a gel. 



Comparison with current opinions on the structure of cytoplasm. The views 

 on the submicroscopic structure of cytoplasm developed in former 

 editions of this monograph have met with some criticism. Before 

 going into this criticism, we shall briefly discuss various points which 

 make our theory fundamentally different from others. 



It is not permissible to draw a parallel between "protoplasmic vis- 

 cosity" and the viscosity of liquids (compare Table XXII, p. 169). 

 For here it is not merely a matter of friction between freely moving 

 particles, but of an additional resistance offered by an elastic, sub- 

 microscopic framework as well. I completely agree with Scarth 

 (1927) when he writes that the fall of a particle through the cytoplasm 

 is comparable to the zig-zag path of shot falling through a brush heap, 

 and that drastic methods like centrifugation forcibly destroy the fine 

 framework of the plasma structure. The work of Scarth also contains 

 the essential points of this monograph in those places where he points 

 out that the polarity and the capacity for growth of cells are incom- 

 patible with the nature of a liquid such as that which has often been 

 attributed to the cytoplasm and the nucleus. 



Often microscopic strands are visible in the cytoplasm. As a dense, 

 tough, "formed" protoplasm, these are embedded in "unformed" 

 protoplasm of semi-liquid consistency. Such differentiations have been 

 distinguished as kinoplasm and matrix (Scarth, 1927), active plasma 

 and paraplasm (v. Mollendorff, 1937) or spongioplasm and en- 

 chylema (Monne, 1942a). In some cases the two constituents can be 

 separated in the centrifuge as a gel rich in lipids and a sol, poor in 

 lipids but rich in mitochondria, comparable to the conditions in the 

 nucleus, where the chromosomal threads and the karyolymph can be 

 separated from each other. The microscopic cytoskeleton (Peters, 

 1937) is not to be identified with the submicroscopic structure. Un- 

 doubtedly the strands which are visible in the ordinary microscope 

 originate from far-reaching bundling of the submicroscopic stra nds 

 postulated by us, but they certainly are not homogeneous and poss ess 



