34 PROTEIDS. 



covered with bubbles of oxygen ; and guaiacum is turned blue by 

 fibrin in presence of hydrogen dioxide or ozonised turpentine. 



When globulin, myosin, and fibrin are compared each with the 

 other, it will be seen that they form a series in which myosin is 

 intermediate between globulin and fibrin. Globulin is excessively soluble 

 in even the most dilute acids and alkalis ; fibrin is almost insoluble in 

 these; while myosin, though more soluble than fibrin, is less soluble 

 than globulin. Globulin again dissolves with the greatest ease in a 

 very dilute solution of sodium chloride. Myosin, on the other hand, 

 dissolves with difficulty ; it is much more soluble in a 10 per cent, than 

 in a one per cent, solution of sodium chloride; and even in a 10 per cent, 

 solution the myosin can hardly be said to be dissolved, so viscid is the 

 resulting fluid and with such difficulty does it filter. Fibrin again 

 dissolves with great difficulty and very slowly in even a 10 per cent, 

 solution of sodium chloride, and in a one per cent, solution it is 

 practically insoluble. When it is remembered that fibrin and myosin 

 are, both of them, the results of clotting, their similarity is intelligible. 

 Myosin is in fact a somewhat more soluble form of fibrin, deposited 

 not in threads or filaments but in clumps and masses. 



CLASS V. Coagulated Proteids. 



These are insoluble in water, dilute acids and alkalis, and neutral 

 saline solutions of all strengths. In fact they are really soluble only 

 in strong acids and strong alkalis, though prolonged action of even 

 dilute acids and alkalis will effect some solution, especially at high 

 temperatures. During solution in strong acids and alkalis a de- 

 structive decomposition takes place, but some amount of acid- or 

 alkali- albumin is always produced, together with some peptone and 

 allied substances. 



Very little is known of the chemical characteristics of this class. 

 They are produced by heating to 100 C., solutions of egg- or serum- 

 albumin, globulins suspended in water or dissolved in saline solutions ; 

 by boiling for a short time fibrin suspended in water, or precipitated 

 acid- and alkali-albumin suspended in water. They are readily 

 converted at the temperature of the body into peptones, by the action 

 of gastric juice in an acid, or of pancreatic juice in an alkaline 

 medium. 



All proteids in solution are precipitated by an excess of strong 

 alcohol. If the precipitant be rapidly removed they are again soluble 

 in water, but if the precipitated proteids are subjected for some time to 

 the action of the alcohol they are, with the exception of peptones, 

 coagulated and lose their solubility. It appears however that the 



