Chapter III 



THE PHYSICAL PROPERTIES AND GENERAL 

 CHARACTERISTICS OF THE CYTOPLASM 



Its appearance in living form:- DUJARDIN, who first studied the 

 cytoplasm in living cells of ciliated Infusoria, has given an abso- 

 lutely exact description of this substance which he calls sarcode, 

 a description which modern observations merely confirm. "This 

 substance", he says, "appears perfectly homogeneous, elastic and 

 contractile, diaphanous and refracting light a little more than 

 water and much less than oil. One can distinguish in it absolutely 

 no trace of organization : neither fibre nor membrane nor an appear- 

 ance of cellular form". 



There is nothing to add to this descrip- 

 tion. The cytoplasm appears to modern 

 observers just as it was described by Du- 

 JARDIN. In living cells, it appears to be a 

 homogeneous substance, as transparent as 

 glass, viscous, a little more refractive than 

 water and non-miscible with it. As has 

 been already stated, modern research has 

 shown that it does, however, always con- 

 tain in suspension numerous granules 

 (chondriosomes, lipide granules) and 

 vacuoles, of which more will be said later. 

 Hence the description of Dujardin can 

 be applied only to the cytoplasm itself, 

 omitting these elements which it contains. 

 For the study of the physical proper- 

 ties of the cytoplasm, the Plasmodium of 

 the Myxomycetes has been much used. It 

 is seen as a voluminous protoplasmic mass 

 of irregular appearance, lobed in the most fanciful manner and 

 enclosing numerous nuclei. This protoplasmic mass changes shape 

 constantly by virtue of the amoeboid movements which control its 

 displacement. It glides along the surface of its support and if this 

 latter be of decaying wood, it worms its way into the interior of 

 the wood, penetrates it only to come out again further on, then to 

 re-enter it, and so on. The huge dimensions of the Plasmodium 

 make it a valuable object for the study of the cytoplasm. The 

 classical experiments successfully perfoiTned by Pfeffer on the 

 Plasmodium of Chondrioderma difforme have shown that in order 

 to alter a small portion of cytoplasm, it is necessary to exert a 

 pressure of 8 mg. per sq. cm. The cytoplasmic strands of this 

 Plasmodium break when subjected to a tension of 120-130 mg. per 

 mm. This indicates a rather strong cohesion which, it may be 

 said, can be even stronger in other types of cytoplasm. 



Fig. 3. — Fragment of a 

 Plasmodium of Chondrioderma 

 diffortne. A, ingested foreign 

 body. X about 50. (After 

 ZOPF) . 



