234 SOAPS AND PROTEINS 



chlorid, combines with water while depriving the sodium oleate 

 of its water or (2) one which acts upon the sodium oleate (like a 

 weak acid) to produce from it a new substance (like fatty acid) 

 which remains emulsified in the unchanged hydrated sodium 

 oleate. In either instance the viscosity of the whole system 

 must rise, as exemplified in the first stages of the salting-out of a 

 soap or in the increase in viscosity observed whenever a " mayon- 

 naise " is made by emulsification of a fat or fat-like body (fatty 

 acid) in a hydrated soap or hydrated protein. With addition of 

 more salt or more fat-like body the type of emulsion changes to 

 one of soap-in-oil and as this occurs the viscosity of the system 

 falls, " serum " separates off and the soap or fatty acid swims as 

 a clot to the top. If the soap or fatty acid is crystalline at, the 

 temperature of the clotting it may, of course, crystallize out. It 

 is of interest therefore to note that in the case of blood coagulation 

 the clot is definitely crystalline. 1 



We do not presume to say which of the two types of " coagu- 

 lant," the " fibrin ferment," rennin or muscle ferment follows, but 

 we incline to the view that it probably acts like a weak acid which 

 splits the original fibrinogen (and not like the salt). The " fer- 

 ment " nature of the different coagulants has been seriously ques- 

 tioned in late" years, for they not only seem heat stabile, but 

 disappear quantitatively as coagulation advances. It is not 

 necessary, of course, that such " splitting " should be induced 

 through a true ferment. The appearance in the reaction mixture 

 of any substance which acts like a weak acid would do quite as 

 well, for the addition of a limited amount of such a substance will 

 not only stiffen a hydrated soap/ water system but, similarly, any 

 hydrated potassium, sodium or other basic proteinate system, as 

 illustrated, for example, in the " souring " of milk. 



How now may the " favoring " action upon coagulation of 

 calcium, iron or other heavier salts be understood? It is necessary, 

 here, to state just which part of the coagulatory process is " fav- 

 ored." Usually it means the earlier appearance of a free clot or 

 the development of a " firmer " clot. Obviously the presence of 

 the heavier metals must favor the development of fatty acid or 

 proteinic acid derivatives which are possessed of low hydration 

 capacities. 



'See STtfBEL: Pfluger's Arch., 166, 361 (1914); W. H. HOWELL: Am. 

 Jour. Physiol., 36, 143 (1914). 



