56 CHEMICAL COMPONENTS OP THE HUMAN BODY. 



gcherer. Mulder. 



Carbon 54.9 53.5 



Hydrogen 7.0 7.0 



Nitrogen 15.7 15.5 



Oxygen ) f 22.0 



Sulphur V 22.4 -I 1.6 



Phosphorus J ( 0.4 



100.0 100.0 



It has lately been affirmed, however, by Prof. Liebig, that Phosphorus is not 

 (like Sulphur) a true constituent of Albumen, or of any of the Protein-com- 

 pounds ; and that it has no existence in any article of food, or in any tissue of 

 the body, save in combination with oxygen as phosphoric acid. 1 Albumen seems 

 never to occur in the animal body, except in such intimate union with fatty and 

 mineral substances, that it is with difficulty separated from them. The quantity 

 of these is variable; but altogether they usually amount to at least 6 per cent., 

 of which from 1 to 2.5 per cent, consists of phosphate of lime. 



21. As a general rule, Albumen is found in all the nutritive fluids of the 

 body, as the Blood, the Chyle, the Lymph, and the serous exudation which 

 percolates through the interstices of the tissues. From several of the tissues, 

 also, it may be obtained in considerable abundance ; but it is not always easy 

 to say whether it is a natural constituent of such tissues, or whether it is simply 

 left by the fluid with which they were charged. It has been recently affirmed 

 by Prof. Liebig, however, that the characteristic solid constituent of Muscle, 

 which has been usually known under the designation of fibrin, is in reality 

 essentially conformable in all its chemical relations with coagulated Albumen ; 

 and is at any rate much more nearly allied to it, than it is to the fibrin of 

 the blood. And if this be true, it is probable that the same may be said of the 

 watts of the component cells of the glandular, nervous, adipose, epidermic, and 

 other tissues, however different may be the character of their contents ; and 

 that Albumen is, in fact, the fundamental constituent of all such tissues as do 

 not belong to the gelatinous type. It cannot be said that Albumen is a normal 

 constituent of any of the secreted fluids, such as the salivary, gastric, or pancre- 

 atic; the peculiar organic constituents of these being apparently albuminous 

 substances in a state of change. And among the proper excretory matters, it 

 is certain that albumen is never found but in consequence of morbid action ; its 

 appearance indicating either disease of the excreting organ, or a marked alter- 

 ation either in the composition of the blood or in the mode of its circulation. 



22. The place of Albumen is occupied in Milk by the substance termed 

 Casein, which seems to differ from it less in ultimate composition, than it does 

 in chemical properties. Casein, like albumen, occurs in the soluble and inso- 

 luble states ; but the passage from one to the other takes place under different 

 conditions. It appears, from the late researches of Scherer and Rochleder, that 

 pure Casein is insoluble in water, and that the soluble casein is a combination 

 of pure casein with an alkaline or earthy base, the withdrawal of which is the 

 cause of its precipitation by acids. 3 In this precipitation, the casein is not 

 reduced to its insoluble form ; as, by neutralizing the acids with alkalies or me- 

 tallic oxides, it again dissolves. Casein is not (like Albumen) made to coagu- 

 late from its ordinary state of solution by the agency of heat ; and the precipi- 

 tate thrown down by the addition of a small quantity of alcohol is readily 

 dissolved again in water. The most characteristic distinctions between Albumen 

 and Casein, however, are afforded by the peculiar action of the lactic and acetic 

 acids, and of the " rennet" of the calf's stomach, upon the latter ; for Casein 



1 See his " Familiar Letters on Chemistry," pp. 437 and 451. 



2 See the Memoir of Dr. Panum, hereafter cited. 



