GENERAL CONSIDERATIONS 19 



occur in nature without a protoplasmic sheath; it may be extremely thin 

 in certain cells,, but it is never entirely wanting. 



Many hypotheses have been advanced to explain the influence of the 

 nucleus and the nature of its reciprocal relations with the protoplasm, but 

 they are yet rather more of a speculative than of an exact scientific nature. 

 The only conclusion which can be drawn with certainty from the discoveries 

 thus far made is that the metabolic processes of the cell go on normally only 

 under the mutual influence of both nucleus and protoplasm, which after all 

 is only a bare statement of the facts in the case. 1 



C. PHYSICAL AND CHEMICAL PROPERTIES OF PROTOPLASM 



Protoplasm appears as a viscous, usually colorless substance which is not 

 miscible with water, and which always contains a varying number of very 

 small, punctiform granules. The distribution of the granules in the cell 

 body is seldom uniform, for one finds as a rule an outermost layer of greater 

 or less thickness free from them. Since this layer is firmer than the inclosed 

 protoplasm containing granules, it is designated as the hyaloplasm (Leydig) 

 in contradistinction to the granular spongioplasm. 



In general it is assumed that resting protoplasm has an alkaline reaction. 

 This appears to be true however only with indicators which are not sensitive 

 to C0 2 : for with indicators which respond to C0 2 , neither animal nor plant 

 cells in the resting state show the alkaline reaction (Friedenthal). But in 

 the case of some lowly organisms e. g., the fission-fungi and the Amoebas 

 the true reaction of the living substance must still appear doubtful, since 

 these are able to live in strongly alkaline nutrient media a circumstance" 

 which does not, however, constitute conclusive proof of an alkaline reaction 

 for the interior of the cell. 



In the gelatinous, colloidal substances (e. g., a solution of gelatin which 

 is drying up through loss of water) with which from a purely physical point 

 of view protoplasm exhibits a close agreement, all possible gradations are 

 met with from the fluid to the solid state, and for such substances the terms 

 " fluid " and " solid " may have within wide limits a purely relative signifi- 

 cance. Hence it is not difficult to understand that views regarding the state 

 of aggregation of protoplasm are very divergent, it being regarded by some 

 authors as solid, by others as fluid. Moreover, it is not to be overlooked that 

 in the endless varieties of differentiations met with in different orders of 

 living beings the state of aggregation may present not insignificant differ- 

 ences. For the cells which exhibit protoplasmic currents (cf. page 21) as well 

 as for the amoeboid cells (cf. page 42) and the egg and early embryonic cells, 

 Rhumbler, with strict regard to the laws which apply to fluids, has adduced 

 weighty reasons for the view that the protoplasm possesses in fact a fluid state 

 of aggregation, and has the mechanical peculiarities of a foam the individual 

 alveoli of which are locally of different constitution. 



1 Spitzer, Loeb and R. S. Lillie have brought forward considerable evidence that the 

 nucleus is the chief agency in the activation of oxygen within the cell. ED. 

 4 



