500 NUTRITION. 



During training, even of the most severe character, not only is great attention paid to 

 diet and exercise, but all of the functions are scrupulously watched. Tranquillity of 

 mind, avoidance of exhaustion, of artificial excitement, stimulants, tobacco, etc., are 

 strictly enjoined; and the process is always very gradual, especially at its commencement, 

 and is continued for several months. The cases in which training has been followed by 

 bad effects are entirely different. Undeveloped boys are frequently trained for boating, 

 in the most reckless manner, until they break down. An attempt is made to accomplish 

 in a few weeks what can only be done physiologically in several months ; and the result 

 is, that some of the vital organs, particularly the heart, are liable to become permanently 

 injured. To improve the " wind " and endurance, a person undergoes the most violent 

 exercise, which is followed by great exhaustion, intense respiratory distress, and disturb- 

 ance of the action of the heart, these parts being suddenly forced far beyond their func- 

 tional capacity. This cannot be done without danger of permanent disturbances of the 

 system, such as have been frequently observed; and it is all the more liable to be followed 

 by bad results, from the fact that amateurs are trained together, five or six under one 

 man, and are more or less independent, while the professional athlete is never out of the 

 sight of his trainer for months, and during that time is under complete control. There 

 is, it seems, every physiological reason to believe that it is beneficial to the general sys- 

 tem to bring it to the highest point of functional activity by training ; but, if this be not 

 done with great caution and judgment, it is liable to be followed by serious results. 



Non-Nitrogenized Principles. The non-nitrogenized principles present a marked 

 contrast to the alimentary substances we have just considered. In the first place, they 

 are not indispensable to the nutrition of all animals. The carnivora, for example, may be 

 well nourished upon a diet composed exclusively of nitrogenized matter ; and the remarks 

 we have just made upon training show that the human subject may be brought to a high 

 condition of physical development, when starch, sugar, and fat are almost entirely elimi- 

 nated from the food. This shows conclusively that the division of the food into plastic 

 and calorific elements is not absolute, and that the animal temperature may be maintained 

 without the hydro-carbons. The nitrogenized principles are probably the only class of 

 alimentary substances capable of forming muscular tissue ; but, by certain transformations, 

 with the exact nature of which we are imperfectly acquainted, this class of substances is 

 capable of producing heat and of furnishing the carbonic acid eliminated in respiration. 

 The non-nitrogenized principles are incapable in themselves of meeting the nutritive 

 demands of the system, and they are either consumed without forming part of the tis- 

 sues or are deposited in the form of fat. These questions we have already considered 

 under the head of alimentation ; and it will be remembered that, with a few exceptions, 

 fat always exists in the body uncombined, either in the form of adipose tissue or of fatty 

 granulations in the substance of other tissues. 



The non-nitrogenized elements taken up by the blood may be divided into two varie- 

 ties : one, the sugars, composed of carbon with hydrogen and oxygen in the proportions 

 to form water, constituting the true hydro-carbons ; and the other, the fats, in which the 

 hydrogen and oxygen do not exist in the proportion to form water. "We speak of the sugars 

 only, because starch and all varieties of sugar taken as food are transformed into glucose. 



In connection with the study of alimentation and glycogenesis, -we have already 

 referred to the destination of the true hydro-carbons in the organism. They are taken 

 as food to a considerable extent, particularly in the form of starch, and are formed con- 

 stantly by the liver in all classes of animals. Sugar is never discharged from the body 

 m health, nor is it deposited in any part of the organism, even as a temporary condition. 

 It generally disappears in the passage of the blood through the lungs. In studying the 

 changes which sugar is capable of undergoing, it has been found that it may be converted 

 into lactic acid or be changed into carbonic acid and water ; but precisely to what extent 

 the sugars undergo these changes, or how they are acted upon by the inspired oxygen, it 



