DIGESTION AND RELATED FUNCTIONS. 797 



paring meat, because it withdraws not only salts of importance, 

 but proteids and the extractives — nitrogenous and other. Beef- 

 tea is valuable chiefly because of these extractives, though it also 

 contains a little gelatin, albumin, and fats. Salt meat furnishes 

 less nutriment, a large part having been removed by the brine ; 

 notwithstanding, all persons at times, and some frequently, find 

 such food highly beneficial, the effect being doubtless not confined 

 to the alimentary tract. 



Meat, according to the heat employed, may be so cooked as to 

 retain the greater part of its juices within it or the reverse. 

 With a high temperature (65° to 70° C.) the outside in roasting 

 may be so quickly hardened as to retain the juices. 



In feeding dogs it is both physiological and economical to give 

 the animal the broth as well as the meat itself. The poor man 

 may get excellent food cheaply by using not alone the meat of the 

 shank of beef, but the soup (extractives) derived from it. There 

 is much waste not only by the consumption of more food than is 

 necessary, but by. the purchase of kinds in which that important 

 class, the proteids, comes at too high a price. 



It is remarkable in the highest degree that man's appetite, or 

 the instinctive choice of food, has proved wiser than our science. 

 It would be impossible even yet to match, by calculations based 

 on any data we can obtain, a diet for each man equal upon the 

 whole to what his instincts prompt. With the lower mammals 

 we can prescribe with greater success. At the same time chemi- 

 cal and physiological science can lay down general principles 

 based on actual experience, which may serve to correct some arti- 

 ficialities acquired by perseverance in habits that were not based 

 on the true instincts of a sound body and a healthy mental and 

 moral nature; for the influence of the latter can not be safely 

 ignored even in such discussions as the present. These remarks, 

 however, are meant to be suggestive rather than exhaustive. 



We may with advantage inquire into the nature of hunger and 

 thirst. These, as we know, are safe guides usually in eating and 

 drinking. 



After a long walk on a warm day one feels thirsty ; the mouth 

 is usually dry ; at all events, moistening the mouth, especially the 

 back of it (pharynx), will of itself partially relieve thirst. But if 

 we remain quiet for a little time the thirst grows less, even if no 

 fluid be taken. The dryness has been relieved by the natural se- 

 cretions. If, however, fluid be introduced into the blood either 

 directly or through the alimentary canal, the thirst is also relieved 

 speedily. The fact that we know when to stop drinking water 

 shows of itself that there must be local sensations that guide us, 

 for it is not possible to believe that the whole of the fluid taken 

 can at once have entered the blood. 



