102 PHYSIOLOGY FOR DENTAL STUDENTS. 



the ' ' factor of safety. ' ' "We have two lungs, although it is quite 

 possible to live with one only, two kidneys, although one will 

 usually suffice, and so with protein in food, we could get along 

 for some time with about half of what we take, but at the con- 

 stant risk of a deficiency, for should physical exhaustion occur, 

 a reserve of building stones ought to be available to restore the 

 tissue which has been consumed. Instead of the excess of pro- 

 tein throwing a strain on the organism, the contrary is the caso, 

 for it is indisputably a greater strain for the tissues to have to 

 construct new building stones than to use these supplied ready 

 made in the food. 



Another deduction which we may draw from these observa- 

 tions is that more protein should be taken when its source is 

 mainly vegetable food than when it is animal. On the other 

 hand, there is nothing to indicate that one kind of animal pro- 

 tein possesses any advantages over another; flesh protein, milk 

 protein, egg protein are practically of equal dietetic value, and 

 with regard to what varieties of meats whether light or dark- 

 are most nutritious, all we can say is that any differences that 

 may be thought to exist are not due to differences in the chemical 

 nature of the proteins which they contain, but depend on their 

 flavor and digestibility. There are more fads and fancies about 

 what meats are nutritious and what are not so than would fill a 

 volume, but after all the whole question is one of flavor. Man 

 digests best what he likes best, and he thrives best when digestion 

 is good. Doctors and dentists must be ready to discuss questions 

 of diet, for the public likes to be treated with something more 

 than the hard facts of science; he demands something mystical 

 and mysterious besides ; if he agrees to be fed according to calorie 

 and protein values, he demands besides that he be told fairy 

 tales about some peculiar virtues which this or that variety of 

 foodstuff possesses. 



Very practical conclusions may be drawn from these observa- 

 itons regarding the most suitable diet for the city dweller. It is 

 evident that we are now-a-days in possession of a sufficient 

 amount of scientific information regarding both the daily require- 

 ments of the body and the ability of the various foodstuffs to 



