. 36 



ANIMAL CHEMISTRY. 



account of this very identity of composition. 

 Hence the opinion is not unworthy of a 

 closer investigation, that gelatine, when 

 taken in the dissolved state, is again con- 

 verted, in the body, into cellular tissue, 

 membrane and cartilage; that it may serve 

 for the reproduction of such parts of these 

 tissues as have been wasted, and for their 

 growth. 



And when the powers of nutrition in the 

 whole body are affected by a change of the 

 health, then, even should the power of form- 

 ing blood remain the same, the organic force 

 by which the constituents of the blood are 

 /transformed into cellular tissue and mem- 

 branes must necessarily be enfeebled by 

 sickness. In the sick man, the intensity of 

 the vital force, its power to produce meta- 

 morphoses, must be diminished as well in 

 the stomach as in all other parts of the body. 



In this condition, the uniform experience of 

 practical physicians shows that gelatinous 

 matters in a dissolved state exercise a most 

 decided influence on the state of the health. 

 Given in a form adapted for assimilation, 

 they serve to husband the vital force, just 

 as may be done, in the case of the stomach, 

 by due preparation of the food in general. 

 Brittleness in the bones of graminivorous 

 animals is clearly owing to a weakness in 

 those parts of the organism whose function 

 it is to convert the constituents of the blood 

 into cellular tissue and membrane ; and if 

 we can trust to the reports of physicians 

 who have resided in the East, the Turkish 

 women, in their diet of rice, and in the fre- 

 quent use of enemata of strong sotfp, have 

 united the conditions necessary for the 

 formation both of cellular cissue and of 

 fat. 



PART II. 



THE METAMORPHOSIS OF TISSUES. 



1. THE absolute identity of composition 

 in the chief constituents of blood and the ni- 

 trogen ked compounds in vegetable food 

 would, some years ago, have furnished a 

 plausible reason for denying the accuracy of 

 the chemical analysis leading to such a re- 

 sult. At that period, experiment had not as 

 yet demonstrated the existence of numerous 

 compounds, both containing nitrogen and 

 devoid of that element, which with the 

 greatest diversity in external characters, yet 

 possess the very same composition in 100 

 parts; nay, many of which even contain the 

 same absolute amount of equivalents of each 

 element. Such examples are now very fre- 

 quent, and are known by the names of 

 isomeric and polymeric compounds. 



2. Cyanuric acid, for example, is a nitro- 

 genized compound which crystallizes in 

 beautiful transparent octahedrons, easily so- 

 luble in water and in acids, and very per- 

 manent. Cyamelide is a second body, abso- 

 lutely insoluble in water and acids, white 

 and opaque like porcelain or magnesia. 

 Hydrated cyanic acid is a third compound, 

 which is a liquid more volatile than pure 

 acetic acid, which blisters the skin, and can- 

 not be brought in contact with water with- 

 out being instantaneously resolved into new 

 products. These three substances not only 

 yield, on analysis, absolutely the same rela- 

 tive weights of the same elements.! but they 

 may be converted and reconverted into one 

 another, even in hermetically closed vessels 

 that is, without the aid of any foreign 

 matter. (See Appendix, 21.) Again, among 

 those substances which contain no nitrogen, 

 we have aldehyde, a combustible liquid mis- 

 cible with water, which boils at the tempe- 

 rature of the hand, attracts oxygen from the 

 atmosphere with avidity, and is thereby 



changed into acetic acid. Tins compound 

 cannot be preserved, even in close vessels : 

 for after some hours or days, its consistence, 

 its volatility, and its power of absorbing 

 oxygen, all are changed. It deposits long, 

 hard, needle-shaped crystals, which at 212 

 are not volatilized, and the supernatant liquid 

 is no longer aldehyde. It now boils at 140, 

 cannot be mixed with water, and when 

 cooled to a moderate degree crystallizes in a 

 form like ice. Nevertheless, analysis has 

 proved, that these three bodies, so different 

 in their characters, are identical in composi- 

 tion. (21.) 



3. A similar group of three occurs in the 

 case of albumen, fibrine, and caseine. They 

 differ in external character, but contain 

 exactly the same proportions of organic ele- 

 ments. 



When animal albumen, fibrine, and ca- 

 seine are dissolved in a moderately strong 

 solution of caustic potash, and the solution 

 is exposed for some time to a high tempera- 

 ture, these substances are decomposed. The 

 addition of acetic acid to the solution causes, 

 in all three, the separation of a gelatinous 

 translucent precipitate, which has exactly 

 the same characters and composition, from 

 whichever of the three substances above 

 mentioned it has been obtained. 



Mulder, to whom we owe the discovery 

 of this compound, found, by exact and care- 

 ful analysis, that it contains the same organic 

 elements, and exactly in the same propor- 

 tion, as the animal matters from which it is 

 prepared ; insomuch, that if we deduct from 

 the analysis of albumen, fibrine, and caseine, 

 the ashes they yield when incinerated, as 

 well as the sulphur and phosphorus they 

 contain, and then calculate the remainder 

 for 100 parts, we obtain the same result an 



