498 NUTRITION. 



and non-nitrogenized; and, although they both disappear in the organism, they possess 

 certain marked differences in their properties, and probably, also, in their relations to 

 nutrition. 



Nitrogenized Principles.- -The nitrogenized principles, having for their basis, carbon, 

 hydrogen, nitrogen, and oxygen, undergo, in the process of digestion and absorp- 

 tion, remarkable changes ; but these are more marked as regards their properties than 

 their ultimate chemical composition. They are all converted into the nitrogenized ele- 

 ments of the blood, which, in their turn, are transformed into the characteristic nitro- 

 genized principles of the different tissues, and are appropriated by these tissues, to sup- 

 ply the place of worn-out matter. With the intimate nature of this series of transfor- 

 mations, we are entirely unacquainted; but we know that the deposition of new 

 nitrogenized matter in the tissues, constituting one of the most important of the acts of 

 nutrition, is attended with a corresponding loss of matter that has become changed into 

 the nitrogenized elements of excretion. It is the intermediate series of phenomena that 

 is so obscure. 



The nutrition of the nitrogenized elements of the tissues may be greatly modified by 

 the supply of new matter. For example, a diet composed of nitrogenized matter in a 

 readily assimilable form will undoubtedly affect favorably the development of the corre- 

 sponding tissues of the body ; and, on the other hand, a deficiency in the supply will pro- 

 duce a corresponding diminution in power and development. The modifications in nutri- 

 tion due to supply have, however, certain well-defined limits. An excess taken as food 

 is not discharged in the faeces, nor does it pass out in the form in which it entered, in 

 the urine ; but it apparently undergoes digestion, becomes absorbed by the blood, and 

 increases the quantity of uitrogenized excrementitious matter discharged, particularly 

 the urea. This fact is shown by the great increase in the elimination of urea produced 

 by an excess of nitrogenized food. Whether the nitrogenized matter that is not actually 

 needed in nutrition be changed into urea in the blood, or whether it be appropriated by 

 the tissues, increasing the activity of their disassimilation, is a question difficult to deter- 

 mine experimentally. Certain it is, however, that an excess of nitrogenized food is 

 thrown off in nearly the same way as an excess of inorganic matter ; the difference being 

 that the latter passes out in the form in which it has entered, and the former is discharged 

 in the form of nitrogenized excrementitious matter. 



Development of Power and Endurance ly Exercise and Diet (Training). The nutrition 

 of the nitrogenized elements of the body is greatly influenced by functional exercise. 

 This is partly local and partly general in its effects. For example, by the persistent 

 exercise of particular muscles, their development can be carried to a high degree of per- 

 fection, the rest of the muscular system undergoing no change ; or the entire muscular 

 system may, by appropriate general exercise, be made to increase considerably in volume, 

 and a person may become capable of great endurance, under an ordinary diet. It is sur- 

 prising, sometimes, to see how small an amount of well-regulated exercise will accomplish 

 this end. But, if it be desired to attain the maximum of strength and endurance, it is 

 necessary to carefully regulate the diet as well as the exercise. Those who are in the 

 habit of " training " men, particularly for pugilistic encounters, have long-since demon- 

 strated practically certain facts which physiologists have been rather slow to appreciate. 

 By carefully regulating the diet, confining it chiefly to nitrogenized articles, eliminating 

 fat entirely, and reducing the starchy elements to the minimum ; by regulating the exer- 

 cise so as to increase the nutritive activity of all the muscles to the greatest possible 

 extent ; by increasing the respiratory activity by running, etc., and removing from the 

 body all the unnecessary adipose tissue ; by all these means, which favor nutritive assimi- 

 lation by the nitrogenized elements of the organism, a man may be " trained " so as to be 

 capable of immense muscular effort and endurance. 



