no PRINCIPLES OF GENERAL PHYSIOLOGY 



structures known as geh. This has been shown in some cases to depend on a 

 redistribution of phases, so that the more solid one changes from the position of 

 internal or dispersed phase to that of external or continuous phase. 



Another important character of emulsoids is that of imbibition, by which they 

 take up large amounts of water, swelling in the process, and exercising considerable 

 force. Acids and alkalies increase the amount of water taken up in the process. 

 The effect of neutral salts in the main follows the same law as the precipitating 

 action, but it seems necessary to assume an additional factor, probably adsorption. 



In imbibition, there are probably two processes at work, one the condensation 

 of water on the surfaces of the colloidal elements, the other, solution of the water 

 in the substance of the particles. No doubt the relative part played by each 

 varies with the amount of water at the disposal of the colloid. 



Imbibition is incapable of explaining the changes of volume of living cells 

 under the action of crystalloids. 



Proteins are emulsoids and obey the same laws as other members of the class. 

 As amphoteric substances, they form salts with strong acids or bases, which salts 

 are electrolytically dissociated. In the first case the protein ion, colloidal, is the 

 positive one, so that the particles forming the internal phase will possess positive 

 charges ; in the second case, it will be the negative one. 



Since the acidic and basic groups may not be of exactly equal strength, proteins 

 are sometimes naturally electrically charged by surface ionisation of the kind 

 described above. 



The effects of acid and alkali on the physical properties may be accounted for 

 by the properties of the protein ion, formed in various relative amounts in 

 different cases. 



Certain proteins are capable of a change, known as "denatu ration," in which 

 their properties approximate to those of a suspensoid, especially in regard to their 

 sensitiveness to electrolytes, in accordance with Hardy's rule of valency. 



The phenomena of aggregation and mutual action, presented by mixtures of 

 colloids and crystalloids, offer great complexity and are of much importance in 

 physiological problems, although as yet very inadequately worked out. 



LITERATURE 



General. 



Wo. Ostwald (1909). Freundlich (1909, pp. 291 to end). Zsigmondy (1905). 

 Hatschek (1913). Graham (1861). 



Brownian Movement and the Kinetic Theory. 

 Perrin (1910). 

 Ramsay, " Elements and Electrons. " London, Harper, 1912, pp. 79-111. 



Emulsoids. 

 Mines (1912). 



Proteins. 



Pauli (1912). 



Chick and Martin (1910 and 1912). 



Hardy, "Colloidal Solutions. The Globulins," Journ. of Physi of. , 33, 251-337. 



Dark Ground Illumination. 



Siedentopf (1913), " Uebungen z. wissensch. Mikroscopie," Heft 1. " Dunkel- 

 feldbeleuchtung." Leipzig, Hirzel. 



Preparation. 



Svedberg(1909, 1). 



