CHEMICAL BASIS OF THE ANIMAL BODY. 1177 



coagulates at 55 — 56°, but in addition one may be obtained 

 coagulating at 59 — 60°, the two differing further in their 

 solubilities in 1 and 10 p.c. solutions of NaCl. These changes 

 are brought about by the salts in the entire absence of any 

 putrefactive phenomena, and the resulting globulins cannot be 

 made to yield fibrin again by any treatment with fibrin-ferment. 



When fresh unboiled fibrin is simply washed till it is white 

 and digested with pure active trypsin, it is largely converted 

 into coagulable proteids during the initial stages of the ferment 

 action. These proteids are characteristically globulins, and one 

 is closely related to paraglobulin, as judged of by its coagulating 

 in saline solutions at 75 . The second coagulates at 55 — 56°, 

 and in this respect more closely resembles fibrinogen. 



The purest fibrin always leaves a small but fairly constant 

 ash-residue on incineration. Of the inorganic constituents of 

 which this residue is composed it is probable that sulphur is 

 the only element which enters essentially into the composition 

 of the fibrin.. 



When boiled in water or treated for some time with alcohol 

 it loses its elasticity, becomes much more opaque, is much less 

 soluble in the various reagents which dissolve the original fibrin 

 with comparative ease, is attacked with much greater difficulty 

 by pepsin and trypsin, and is in fact indistinguishable from all 

 other coagulated proteids. 



A peculiar property of this body remains yet to be men- 

 tioned, viz. its power of decomposing hydrogen dioxide. Pieces 

 of fresh fibrin placed in this fluid, though themselves under- 

 going no change, soon become covered with bubbles of oxygen ; 

 and guaiacum is turned blue by fibrin in presence of hydrogen 

 dioxide or ozonized turpentine. 



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 solu- 

 tion in strong acids and alkalis a destructive 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 dis- 

 solved 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 tern- 



