CHEMICAL COMPOSITION OF THE TISSUES. 81 



The chemical composition of the teeth, of the different glands, and 

 of the various secretions, will be mentioned, with their uses and actions, 

 in the physiological section of this work. 



In reviewing what has been said concerning the proximate chemical 

 substances which compose the various tissues of the body, one cannot 

 fail to be struck with the fact that, with the exception of bone, in 

 which the quantity is small, water enters so largely into the constitu- 

 tion of them all. Indeed, according to Moleschott, it forms about 68 

 parts out of 100 in the entire human body. The remaining 32 parts 

 per cent, of dried substances consist, in round numbers, of 15 parts 

 of albuminoid bodies, including albumen, globulin, syntonin, fibrin, 

 and coloring substances, 5 parts of gelatinous and chondrinous sub- 

 stances, 2.5 of fatty matters, .5 of all the different extractive sub- 

 stances, including organic acids, sugar, and urea, and lastly, of 9 

 parts of salts, of which 1 perhaps is alkaline, and 8 are earthy. 



The albumen and globulin are found, as will have been noticed, 

 chiefly in the blood, chyle, lymph, nervous substance, and muscle ; 

 the syntonin and fibrin in the muscles, the blood, the chyle, and 

 the lymph ; the coloring matters in the blood, the eyes, the hair, and 

 the bile ; the gelatinous and chondrinous substances in the areolar 

 and fibrous connective tissues, in the skin, the bones, and the carti- 

 lages ; horny substances in the epidermis, nails and hairs ; fatty sub- 

 stances in the adipose tissue, the brain, the blood, the chyle, and the 

 bile ; and extractive matters in most of the tissues and organs of the 

 body. Of the alkaline and earthy salts, all occur in the blood ; but 

 the lime-salts are found principally in the bones and teeth, and much 

 more scantily in cartilage ; the magnesia salts occur in the bones, in 

 the muscles, and in the blood; the soda salts, especially the chloride 

 of sodium, in every tissue, but markedly in the blood-plasma ; whilst 

 the potash salts are found in the blood-corpuscles, and in the muscles. 

 The fluoride of calcium exists in the bones, in the teeth, and in milk ; 

 silica, chiefly in the bones and the hair ; and iron principally in the 

 blood. Carbonic acid and oxygen must occur everywhere, but mainly 

 in the blood. 



As to the water, combined in various measure with every tissue of 

 the body, it is just as important, in regard to their chemical constitu- 

 tion and reactions, as we have seen it to be in reference to their phys- 

 ical characteristics, such as their softness, elasticity, and permeability. 

 This contained or essential water, or tissue-water, as it might be called, 

 also facilitates in an extraordinary manner, by its universal solvent 

 power, all the requisite and incessant chemical changes which, we 

 know, take place, not only in the more fluid, but also in the most solid 

 parts of the living body. It is probable, also, that, just as in certain 

 aqueous solutions of salts or other substances, the water appears often 

 to be chemically combined with those substances, and not to be a 

 mere solvent, so, in the changes from the solid to the fluid, or from 

 the fluid to the solid state, of certain constituents of the body, water 

 enters into combination with them, or leaves its state of combination 

 with them, in definite proportions at various times. The vast impor- 



