Guilliermond - Atkinson — 32 — Cytoplasm 



form hydrosols, from the hydrophilic colloids whose micelles 

 have a strong affinity for water and produce solutions which are 

 optically void (fluid hydrogels of Mayer and Schaeffer). Other 

 authors have reserved for this latter group the name isocolloids and 

 differentiate between the semi-fluid state or isocolloidal hydrogel 

 and the fluid state or isocolloidal hydrosol. 



The structure of the hydrogels is, moreover, variously inter- 

 preted. Certain authors consider the hydrogel as formed by an 

 assemblage of micelles lying more or less closely together and 

 heavily saturated with water (Bradford). Others consider it as 

 constituted of a network holding water in its alveoli (Hardy). 

 Still others including Procter, Wilson, Jacques Loeb, think that 

 there is no difference between a true solution and a protein hydro- 

 gel. They believe that the protein hydrogel is made up of a homo- 

 geneous dispersion of protein and water molecules, their propor- 

 tional amounts varying greatly and regulating the consistency of 

 the system. Lumiere, elaborating on this conception, separated 

 into two categories the substances which until then had been desig- 

 nated as colloidal : first, the micelloid colloids, in the state of hydro- 

 sols, formed of voluminous polymolecular particles and visible in 

 the ultramicroscope and second, molecular colloids, characterized 

 by the optically void state of their solution, formed of monomolec- 

 ular particles and taking on, as they solidify, the aspect of glue. 

 These last, according to Lumiere's view, are in reality true solu- 

 tions, distinguished from solutions of crytalloids only by the 

 enormous dimensions of their molecules to which they owe their 

 special properties. 



Devaux, who shared this opinion, looks upon these colloids as 

 allied to strongly polymerized compounds, such as cellulose and 

 rubber recently studied by Staudinger, which Devaux considers 

 as formed of molecules characterized by being extraordinarily long 

 but still conserving transversely the dimensions of ordinary mole- 

 cules, i.e., molecules arranged in a line. This, according to De- 

 vaux, explains their colloidal properties, for example their ability 

 to swell up in certain liquid media and give viscous and ropy solu- 

 tions. Certain reasons would seem to support this opinion. It is 

 known, in fact, that two molecules of amino acids may combine by 

 peptide bonds and, by repetition of the process, form a long chain 

 constituted of molecules arranged in lines carrying laterally, like 

 oars, the radicals of various amino acids. Several polypeptides may 

 combine in this way to give a very long chain, straight or folded 

 over, such as keratin which, according to the work of Astbury, 

 shows linear molecules (X-ray patterns). The knowledge of pro- 

 tein structure is not far enough advanced so that it can be known 

 whether generalization can be made from this structure to include 

 cytoplasmic proteins. Nevertheless, some biologists recognize the 

 existence of the fibrillar structure and crystalline nature of organic 

 gels and in particular of the cytoplasm (Seifriz). This structure 

 would permit them to explain, in accordance with Seifriz's opin- 

 ion, both the pulsations observed in the Plasmodia of Myxomycetes 



