FIBRINE. 89 



Origin. Caseine is probably formed in the blood (of women) 

 from albuminose and albumen, but nothing certain is known on 

 this subject ; and that obtained from the milk of different animals 

 so varies in its properties, that Lehman n suggests that "caseine is 

 not a simple organic body, but a mixture of at least two different 

 substances. It is, also, a highly transmutable substance, often un- 

 dergoing change on the application of the mildest reagents." 



Uses. Caseine exists in two forms in milk : 1. It forms the in- 

 vesting membrane 1 of the milk-globules, as proved by Henle and 

 E. Mitscherlich. 2. Most of it is dissolved in this fluid. 



Caseine, taken as food, probably, like albumen, is converted into 

 albuminose in the small intestine, and is finally disposed of in the 

 same manner. (See p. 86.) 



Thus all the tissues of the young mammalia are developed for a 

 time after birth from the caseine (and other elements) of milk, as 

 those of birds are from the yolk of the egg. 2 It is soon coagulated 

 by the action of the gastric fluid, and takes the form of curd, and 

 cannot then be distinguished from coagulated albumen. The "curd- 

 ling" of milk, therefore, in an infant's stomach, is no sign of disease, 

 as is often incorrectly asserted. 



The large quantity of phosphate of lime in milk adapts this fluid 

 to the necessities of the young animals while the bones are under- 

 going rapid development. In adults, a less amount in the albumen 

 of the blood is sufficient for their nutrition. 



Kiesteine, a substance forming a thick pellicle, generally exhaling 

 the odor of decomposing cheese, upon the urine of pregnant women, 

 has been regarded as being allied to caseine, and as probably result- 

 ing from its decomposition. But Lehmann maintains that the layer 

 is merely a formation of crystals of triple phosphate and fungoid 

 and confervoid growths, which takes place when the urine becomes 

 alkaline. Still, the urine of pregnant women is more likely to pre- 

 sent it, though it is not peculiar to pregnancy. It occurs, also, in 

 hysteria and chlorosis, and results from an increased tendency to 

 alkaline fermentation. 



4. Fibrine. 



Fibrine is found, in its natural fluid state, in blood (.19 to .28 per 

 cent.), chyle, and lymph (.052 per cent.), and in inflammatory exu- 



1 Sulphate of soda causes the membrane to burst when the inclosed fat is set free. 



2 Lehmann believes that the vitelline substance forming the albuminous body of 

 the yolk of eggs is a mixture of albumen and caseine. 



