FAMILIAR LETTERS ON CHEMISTRY. 3} 



bones, the membranes, the cells, and the skin, suffer in the animal body, under the 

 influence of oxygen and moisture, a progressive alteration; a part of these tissues 

 is separated, and must be restored from the blood ; but this alteration and restora- 

 tion is obviously confined within very narrow limits. 



While, in the body of a starving or sick individual, the fat disappears, and the 

 muscular tissue takes once more the form of blood, we find that the tendons and 

 membranes retain their natural condition ; the limbs of the dead body retain their 

 connexions, which depend on the gelatinous tissues. 



On the other hand, we see that the gelatine of bones devoured by a dog entirely 

 disappears, while only the bone earth is found in his excrements. The same is 

 true of a man, when fed on food rich in gelatine, as for example, strong soup. The 

 gelatine is not to be found either in the urine or in the faeces, and consequently 

 nir.st have undergone a change, and must have served some purpose in the animal 

 economy. It is clear that the gelatine must be expelled from the body in a form 

 different from that in which it was introduced as food. 



When we consider the transformation of the albumen of the blood into a part of 

 an organ composed of fibrine, the identity in composition of the two substances 

 renders the change easily conceivable. Indeed, we find the change of a dissolved , 

 substance into an insoluble organ of vitality, chemically speaking, natural and 

 easily explained, on 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 converted, in the body, into celular tissue, membrane, and 

 cartilage ; that it may serve for the re-production 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 effected by a change of 

 the health, then, even should the power of forming blood remain the same, the 

 organic force by which the constituents of the blood are transformed into cellular 

 tissue and membranes must necessarily be enfeebled by sickness. In the sick man,'! 

 the intensity of the vital force, its power to produce metamorphoses, must be J 

 diminished as well in the stomach as in all other parts of the body. In this con- 

 dition, the uniform experience of practical physicians shows that gelatinous mat- 

 ters, 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 frequent use of enemata of strong soup, have united the conditions 

 necessary for the formation both of cellular tissue and of fat. 



LETTER XI 



MY DEAR SIR : 



In the immense, yet limited expanse of the ocean, the animal and vegetable 

 kingdoms are mutually dependent upon, and successive to, each other. The animals 

 obtain their constituent elements from the plants, and restore them to the water in 

 their original form, when they again serve as nourishment to a new generation of 

 plants. 



The oxygen, which marine animals withdraw in their respiration from the air, 

 dissolved in sea-water, is returned to the water by the vital processes of sea plants ; 

 that air is richer in oxygen than atmospheric air, containing thirty-two to thirty- 

 three per cent., while the latter contains only twenty-one per cent. Oxygen also 

 combines with the products of the putrefaction "of dead animal bodies, changes their 

 carbon into carbonic acid, their hydrogen into water, and their nitrogen assumes 

 again the form of ammonia. 



Thus we observe in the ocean a circulation takes place without the addition or 

 abstraction of any element, unlimited in duration, although limited in extent, 

 inasmuch as in a confined space the nourishment of plants exists in a limited 

 quantity. 



