124 STUDIES IN PHYSIOLOGY 



foods are the essential conditions. Every one is familiar with 

 the fact that the face looks pale after loss of sleep, or 

 when food and fresh air are insufficient, or during periods 

 of physical inactivity, and this appearance indicates a lack 

 of red corpuscles. Habitual paleness, or a-nai'mi-a, is a 

 disease requiring medical treatment. It is frequently due to 

 a want of iron in the system ; hence, the efficacy of tonics 

 containing this element. Fresh air, a moderate amount of 

 exercise, and good food are usually the best remedies for 

 ansemia. A good complexion is, therefore, very largely 

 dependent on healthy blood. Paint, powder, and other 

 cosmetics will not give such a complexion ; and besides 

 cheapening the individual who uses them habitually, they 

 are often a source of permanent injury to the skin and 

 blood. 



Conditions affecting the Serum All the nutrition of the 



tissues is derived from the blood, and all the nutrients of 

 the blood come from the foods we eat. If these foods are 

 insufficient or of an improper kind, the serum will of course 

 be deprived of necessary ingredients, and the organs must 

 inevitably suffer in consequence. Hunger and thirst are the 

 sensations that tell us the blood is in need of new material 

 (see p. 294). That this is true is proven conclusively by the 

 fact that these sensations disappear when water and liquid 

 food, instead of being swallowed, are injected directly 

 through the skin into the blood vessels. In supplying 

 material for the blood, however, one must not follow en- 

 tirely the dictates of taste. For instance, if one is very 

 thirsty, one is tempted to drink rapidly a great quantity 

 of ice-cold liquid, when a smaller quantity of water, in 

 passing slowly through the mouth, will alleviate the thirst 

 much sooner and more completely. The importance of eat- 

 ing proteid foods cannot be emphasized too often. Healthy 

 blood should contain 8 % to 9 % of this kind of nutrient, 

 and its place can never be filled by the sometimes more 

 palatable sugars, starches, or fats. 



