104 HOW CROPS GROW. 



a curdy coagulumis formed, which agrees in its properties 

 with casein. (Bopp, Ann. Gh. Ph., 60, p. 30 ; Gunning, 

 Jour, fur Prakt. Chem., 69, p. 52.) 



Lehmann has shown that when albumin is dissolved in 

 potash, and mixed with a little milk-sugar and oily fat, the 

 mixture coagulates with rennet exactly as milk curdles. 

 (Gorup-Besanez, Phys. Chem., p. 139.) 



Sullivan has observed that the casein of milk which waa 

 kept in closed air-tight vessels for a long time, at first co 

 agulated, but afterward dissolved again to a nearly clear 

 liquid, which was found to contain no casein, but by heat 

 ing, coagulated, showing the conversion of casein into 

 albumin, or a similar body. (Phil. Mag., 4, XVIII, 203.) 



Some maintain that casein is not a distinct albuminoid, 

 but a compound of albumin with potash, containing, ac 

 cording to Lieberkiihn, 5.5| of this alkali. Its peculiarities 

 are in part due to its natural association with phosphate 

 of potash. Kiihne, Phys. Chem., 1868, p. 565. See, how 

 ever, Schwarzenbach, Ann. Ch. u. Ph., 144, p. 63. 



The Albuminoids in Animal Nutrition. We step 

 aside for a moment from our proper plan to direct atten 

 tion to the beautiful adaptation of this group of organic 

 substances to the nutrition of animals. Those bodies which 

 we have just noticed as the animal albuminoids, together 

 with others of similar composition, constitute a large share 

 of the healthy animal organism, and especially characterize 

 its actual working machinery, being essential ingredients 

 of the muscles find cartilages, as well as of the nerves and 

 brain. They likewise exist largely in the nutritive fluids 

 of the animal in blood and milk. So far as we know, :he ~1 

 animal body has not the power to produce a particle of 

 albumin, or fibrin, or casein; it can only transform these&quot; 7 

 bodies as presented to it from external sources. They are 

 hence indispensable ingredients of food, and have been 

 aptly designated by Liebig as the plastic elements of nu 

 trition. It is, in all cases, the plant which originally con- 



