SECOND DIVISION. 



' "% 



THE IMMEDIATE PRINCIPLES OF WHICH THE TISSUES 

 OF THE HUMAN BODY ARE COMPOSED. 



THE immediate principles of the tissues, are the " last bodies con- 

 stituting the organism to which the tissues can be reduced by mere 

 anatomical analysis; and which admit of no further subdivision 

 without chemical decomposition" 1 Sugar, gum, starch, cellulose, 

 water, &c., are immediate principles to a plant; and water, albu- 

 men, fat, urea, &c., to an animal. The carbon, oxygen, hydrogen, 

 &c., composing these are the simple elements, or the elementary (or 

 mediate) principles of the plant, or the animal, respectively. 



The expression, k ' immediate principles," is borrowed from Chev- 

 reul, who thus defends its use: "Some scientific writers think this 

 expression objectionable, since it is not reasonable to apply the 

 word principle to compound bodies. I do not participate in this 

 opinion. For when we consider in a general way the composition 

 of a salt, as established by Lavoisier, it is apparent that it is 

 constituted by the union of an acid and an alkali, rather than by 

 the elements of the acid with those of the alkali, since if these ele- 

 ments are united in other proportions than such as constitute an 

 acid and an alkaline body, they no longer give us the idea of a salt. 

 Hence it seems proper to say that the acid and the alkali are the 

 two immediate principles of the salts. It is the same with sugar, 

 starch, gum, lignine, &c., in respect to a plant, and with fibrine, 

 albumen, &c., in respect to an animal. These substances should be 

 regarded as the immediate principles of the plant or of the animal to 

 which they belong, while oxygen, nitrogen, carbon, and hydrogen 



1 Robin and Verdeil's Anatomical and Physiological Chemistry ; 3 vols. p. 1887, 

 with an Atlas. For an extended review of this work, and many of the facts intro- 

 duced into this division, see the American Medical Monthly, for March, 1855. 



