102 OF FOOD, AND THE DIGESTIVE PROCESS. 



oxidation of the hydrocarbonaceous constituents; the union of these with 

 oxygen, or their combustion, appearing to generate the force which is ren- 

 dered apparent in locomotion or manual labor. Hence it is found that con- 

 siderable, and with healthy muscles even prolonged, exertion can be made 

 on food containing little or no nitrogen as, for instance, on biscuits made 

 of starch and sugar, or starch and fat. General experience, however, as 

 well as the experiments of Dr. Hammond and Mr. Savory as we have 

 already seen and especially those of Dr. Parkes, which will hereafter be 

 more fully discussed, show conclusively that there is a limit to the muscular 

 force which can be exerted under such circumstances; and that when food 

 has been administered which is either altogether deficient in nitrogen, or which 

 contains an insufficient supply of that substance, sooner or later the power of 

 the muscles diminishes, and at length altogether fails. It may therefore be 

 regarded as a well-established fact that when severe and sustained muscular 

 exertion is required to be performed, the food must contain not only a due 

 supply of hydrocarbouaceous and easily oxidizable substance which may 

 develop the muscular force, but also a sufficient amount of nitrogenous 

 material to repair the waste of tissue which occurs in the act of contraction. 

 61. The substances forming the Albuminous group ( 53) are applicable 

 to the support of the Animal body, both by affording the materials for the 

 nutrition and re-formation of its tissues, and also by serving for the main- 

 tenance of its heat, and the production of muscular force, through the de- 

 composition of which they are susceptible, into hydrocarbonaceous matters 

 capable of undergoing direct oxidation, and highly azotized compounds 

 which ultimately pass off by the kidneys. The proportions of carbon, 

 hydrogen, oxygen, and nitrogen, of which all these substances are composed, 

 appear to be very similar; and they seem all capable of being reduced by 

 the digestive process to a like condition. Hence it is a matter of little con- 

 sequence, except as regards the proportion of inorganic matters with which 

 they may be respectively united, whether we draw our histogeuetic materials 

 from the flesh of animals (myosin, syntonin ), from the white of egg (albu- 

 men ), from the curd of milk (casein), from the grain of wheat (gluten), or 

 from the seed of the pea or bean (legumin). Neither of these substances, 

 however, can long sustain life when it is used by itself; for it has been ex- 

 perimentally ascertained, that by being made to feed constantly on the same 

 substance .(boiled white of egg, for instance, or meat deprived of the osma- 

 zome that gives it flavor), an animal may be effectually starved ; its disgust 

 at such food being such, that even if this be swallowed, it is not digested. 

 Thus Dr. Hammond limited himself for a period of ten days to a diet of 

 about 1-i Ib. of albumen obtained from the serum of bullock's blood, and 4 

 Ibs. of distilled water per diem. Little inconvenience was experienced until 

 the fourth day, when loss of appetite, headache, and debility were felt. The 

 severity of these symptoms rapidly increased, and the disgust which the 

 monotony of the diet occasioned was so great, that it was with much diffi- 

 culty the albumen could be eaten. On the seventh day, albumen appeared 

 in the uriue ; and on the ninth, such severe diarrhoea set in that he was 

 compelled to give up the experiment. There was no failure in the maiu- 

 ti'iiaiuv of the temperature of the body, though its weight was notably 

 diminished at the end of the experiment, and the meutal faculties remained 

 clear throughout. The organized fabric of Animals contains also a large 

 quantity of Gelatin-yielding tissues. It seems certain that these tissues 

 may be produced out of fibrin and albumen; since in animals that are sup- 

 ported on these, or at least consume no gelatin with their food, the nutrition 

 of the gelatinous tissues does not seem to be impaired. The experiments of 



