A STUDY OF BLOOD MANUFACTURE 109 



physician and, what is of equal importance, to follow his 

 directions implicitly. 



Effects of Alcoholic Drinks on the Organs of Digestion. Alco- 

 hol, unlike most of the substances taken into the alimentary 

 canal, requires no digestion. It can, therefore, be absorbed 

 very rapidly by the blood, and hence alcohol is probably 

 sometimes of great value when administered by physicians, 

 in cases when ordinary food cannot be digested. In health, 

 however, alcoholic drinks must be regarded as an expensive 

 and extremely dangerous source of energy. 



According to the best authorities, small quantities of 

 alcohol (when sufficiently diluted) seem for an adult to 

 stimulate an increased flow of saliva and gastric juice. 

 The time required for the digestion of food, when alcohol 

 is present, in these small quantities, does not seem to be 

 increased. Entirely different effects follow, however, when 

 strong distilled liquors are taken, and alcohol in any large 

 quantity often produces serious disturbances of the organs 

 of digestion. This is especially true when liquors are taken 

 without food, that is, between meals. The constant danger 

 that the moderate use of beer and the light wines will lead to 

 an uncontrollable thirst for alcohol cannot be emphasized too 

 strongly. All authorities agree, too, that the growing youth 

 should let alcohol entirely alone. 



15. A COMPARATIVE STUDY OF DIGESTION 



A Study of Teeth. Among the various groups of inverte- 

 brates, one finds structures that have a function more or 

 less like that of teeth. Beetles and grasshoppers, for ex- 

 ample, have two horny jaws that move from side to side, 

 which they use to bite their food. In the mouth of the 

 lobster and crayfish similar structures are found, and in 

 addition these animals have strong teeth in the stomach 

 that grind against one another. This arrangement is called 

 a, "gastric mill." Many snails have a great number of mi- 



