CHEMISTRY. 



[DECOMPOSITION, rnx 



As milk contain*, among iU inorganic constituents, 

 :..'. . : . - . . ' ..'..: 



.is the compound* of potash, linn-. 

 ne*ia, and ozido of iron, with phosphoric acid, it i* ap- 

 parent i :ont bate, and tlio most 

 important acids, together with pounds of chlo- 

 10 blood, are reprMented in milk ; that it to 

 ay, all the inorganic substance* to which dim-rent tis- 

 sues poMCM * dmtioct and j-eculiar afliuity, arc there 



r r. -.:,!.. I 



t, 19. Saliva, gaitrio juice, bile, pancreatic and intes- 

 tinal juice, have already boon discussed, according to 

 their several parts in the digestive process. We have 

 v them here also, as they tako aii im- 

 portant place among the substances transuding from the 

 blood, tlirough the walls of the capillaries. An nlbu- 

 iii. nous coiiijM.mii. I, which, from its presence in saliva, 

 has been called the saliva principle (ptyaline), <}>' 

 margaric alkalies, bile-fat, a fat contain :,.,ru, 



and all the inorganic substances vbioh are contained lrl 

 1, cluarly bespeak the origin of saliva, which 

 appears in tho mouth, mixud with mucus. 



In the saliva, as it flows from tho secretory canals of 

 the salivary glands, alkali predominates. Why, at tho 

 same time, the fluids of the mouth are so seldom fn-.m.l 

 acid, is not yet thorouglily known ; as, according to tho 

 most recent researches, even pure mucus of the mouth, 

 unmixed with saliva, appears to possess alkaline pro- 

 perties. 



20. Gastric juice, furnished by the small glands of 

 the stomach, also contains an organic substance, which, 

 like the albuminous matters, is neither alkaline nor 

 acid, but consists of nitrogen, carbon, hydrogen, and 

 oxygen; and is, at nil events, closely allied with the 

 albuminous matters, though it differs from them in some 

 less essential properties. As it cannot be denied that 

 this combination has a highly important influence in 

 dissolving the albuminous substances, the digestion of 

 which is one of tho first conditions of the formation of 

 blood it lias, therefore, not improperly been called. 

 par excellence, tho digestive principle, or pepsin. The 

 digestive principle is, however, very vigorously sup- 

 ported in its dissolving action by a free acid, to which 

 the gastric juice owes the property of reddening litmus. 

 This is to bo considered, according to the most recent 

 investigations, as hydrochloric acid.* 



Among the inorganic substances of gastric juice, we 

 have besides to mention the compounds of clilorino with 

 sodium and potassium, calcium, magnesium, and iron, 

 and with tho phosphoric salts. 



J 21. In the secretion of the liver, there are two 

 peculiar organic acids, one of which, containing only 

 nitrogen, carbon, hydrogen, and oxygen, is called rAo/ic 

 acid ; the other, which, besides tho four elements men- 

 tioned, contains a very inconsiderable quantity of sul- 

 phur, may be called sulphurised cholic acid. Apart 

 from tho liver, no trace of these acids is to bo found in 

 the blood. They are, therefore not elaborated in the 

 general circulation, but by the action of tho liver. 



A sweetish-bitter taste is not only peculiar to these 

 acids, but also to their combinations with sodium. In 

 the latter form they arc Holublu in water. 



Tho combination of both those acids loaves no doubt 

 that the albuminous substances of tho blood ore essential 

 iyir form:'' . and gall-fat, 



accompany tho combination* of potash with cholic 

 and sulphuretted cholic a- 



Tho bilo owes its yellowish-green colour, sometime* 

 inclining to brown and sometimes to green, to H. 

 organic colouring matters containing nitrogen; an 

 alkaline character to phosphate of soda, a salt in which 

 tho alkaline ingredient predominate*. Tho other in- 

 organic substances are common salt, chloride of potas- 

 sium, carbonated alkalies, and the phosphorates of lime, 

 magnesia, and oxide of iron. 



i 22. The pancreatic juice is a fluid containing no much 



men, that it coagulates by heat almost as completely 



as the white of eggs itself. The alkaline property of 



fee uttr, p. 117. 



this secretion, cert (inly, grontly contributes to its carry- 

 ing with it so much albumen from the blood into thu 

 cells of the pancreas* The albumen of the pane: 

 juice, however, does not entirely correspond to that of 

 the blood, both are precipitated by alcohol from i 

 solution in .lry tho albumen of the 



blood which has been prccipittr Alcohol, we can- 



not dissolve it a^ain in water ; while tho albumen of the 

 pancreatic juice is oven tJn n soluble. 



Besides margarine, and some other organic substance* 

 which have been very imperfectly examined, because of 

 the difficulty of procuring pure pancreatic juice, wo lint! 

 in this liquid common .- .11. chloride of potassium, phos- 

 phorates, carboiiato.i, and sulphates of the alka'i. -, ami 

 lime combined with c <1 phosphoric ac 



$ 23. With all digestive fluids is mixed a certain 

 quantity of mucus, which is alkaline in the mouth, and 

 is said to be m-illn T acid nor alkaline in tho empty 

 stomach. In the intestines this mucus is not only mixed 

 with all tho above-mentioned digestive fluids, sa 1 

 gastric juice, bile and pancreatic juice, but contains also 

 a peculiar secretion attracted from the K i tain 



small glands in tho walls of tho intestines. These 

 r, are email, and the quantity of their 

 secretion is scanty ; but the quantity of the other diges- 

 tive fluids mixed with it is abundant. Therefore we 

 kuow of this intestinal juice nothing more than that it 

 possesses alkaline properties. 



Mucus contains, lirst, a peculiar element of which 

 little is known, but from which it d< i-opi-rty of 



cohering in threads; secondly, a number of horny cel- 

 lules, from the inte,ri< final 

 canal ; and finally, a combination of carbonate, phos- 

 phate, and sulphate of soda, phosphate and carbonate of 

 lime, and oxide of iron. 



J 24. 1) -n and Transition. It is a funda- 



mental property of the organic substances of our I ody, 

 that their combinations possess very little peniiain 

 A perpetual process of transition from one state of being 

 to another, constitutes a grand circle, of which the nou- 

 rishment of man himself forms but one little 

 The life of plants and animals is not only a direct result 

 of this constant change of matter, but all organic life is 

 a continuous process of alternate combination at; 

 composition, to which higher and lower influences, co- 

 operating in essential harmony, contribute. Whatp' 

 absorb from the soil and the air, they transform into 

 on which the herbivorous animals feed; and 

 by the latter they are retransformed into animal food for 

 the support of carnivorous classes, as well as for i 

 which feed upon a mixed diet. To the latter class, man 

 himself belongs. Then that which is given oil in an un- 

 interrupted series of various kinds of decomposition by 

 men, animals, and plants, during life and after death, 

 returns again into the air and soil as material for tho 

 growth of another generation of plants. Here again t he. 

 3 of transition recommences, and a perpetual and 

 ceaseless revolution is pursued. 



It is during life itself that this decomposition takes 

 place. In tho very tissues, a regressive metamorphosis, 

 so to speak, has already begun ; for the oxygen of the 

 air, which we incessantly inhale, is conveyed to all parts 

 of our body. Ami no clement exerts a mightier influ- 

 iii the formation anil dissolution of organic com- 

 binations than oxygen. t Exposed to tho continual 

 action of this clement, which all kinds of vegetation 

 are unceasingly giving forth into tho atmosphere,} no 

 organic combination of our bodies can maintain its per- 

 manence. Albumen, gelatine, ami fat, tibrine and 

 sugar, all are gradually rearranged into compounds, 

 containing at every step an increased quantity of oxy- 

 gen. These revert from the ti- a Mood, from 

 which they are attracted by certain glands, collected 

 receptacles, and at last ejected externally. This ejection 

 is called excretion. 



!>.' alHious Bodies with the 



Tisniu. Decomposition continually goes on in the 

 tissues; for what physiologists of a former age hod 



f Bee ante, p. 913. * S ante, p. 315. 



