ALBUMINS OR PROTEINS. 133 



conglutin of the lupins, almonds, nuts, etc., are insoluble; while gliadin, 

 found in wheat, rye, barley, and oats, is soluble. Zein, a protein obtained 

 from corn, is soluble in alcohol. This group of alcohol-soluble albuminous 

 bodies from plant seeds is also characterized by the absence of lysine, in 

 their composition, whereas almost all of the other proteins yield this as 

 a cleavage-product. 



The group of fibrinogens and fibrin is better defined. We shall dwell 

 more in detail on these proteins * later on. They have, in common with 

 casein and myosin, the faculty of being clotted, i.e., changed to a solid 

 state, by a ferment. This curdling is not identical with coagulation. Al- 

 though the curdled proteins are no longer soluble in water, they can still 

 be coagulated, i.e., completely denaturized by heating or by treating them 

 with alcohol. Fibrinogen is found in the blood-plasma of all inverte- 

 brates. It is changed into fibrin by the action of a ferment. The 

 coagulation of blood, which normally occurs only when the blood has left 

 its containing vessels, is dependent on this action. We shall see later 

 that this process is an extremely complicated one which has not yet been 

 explained entirely. 



Myosin acts very much like fibrinogen, and is found in the fibres 

 of striated muscle in a soluble form. Its curdling causes rigor mortis. 

 The cause of the curdling of this muscle material is not understood. A 

 ferment action, analogous to that of fibrin formation, has been offered in 

 explanation, although such a ferment has not yet been proved definitely 

 to exist. We must also mention the fact that besides myosin other 

 albuminous substances, among these myogen, 2 have been described. It 

 is difficult to determine whether these proteins are distinctively-charac- 

 terized albuminous substances, or, more probably, the same myosin in 

 different forms. We have seen that many proteins, including mycsin, 

 can be very easily denaturized. These products, therefore, have entirely 

 different properties, and easily give one the impression of containing a 

 protein of a peculiar nature. We cannot go far astray if we confine our- 

 selves, at least for the present, to calling them simply, " muscle-albumins." 

 We also find these same substances in the smooth muscles. Analogous 

 proteins must be present in other organs, as they also show the same 

 rigor mortis phenomenon. This, however, gradually disappears. No 

 satisfactory explanation of this process has as yet been presented. 



We will now discuss a group of proteins whose distinctive characteristic 

 is the presence of phosphorus. This group of nucleo-albumins includes 

 a very heterogeneous collection of proteins. They also possess another 

 lesser characteristic in being largely liquefied by pepsin-hydrochloric acid 

 digestion, the complex containing phosphorus being split off and finally 



1 Cf. the Lecture on Blood. 



2 O. von Fiirth: Ergeb. Physiol. (Asher and Spiro) 1, 110 (1902). 



