166 ANATOMY AND PHYSIOLOGY. 



Condiments, as spices, though they may at first excite the action 

 of a debilitated stomach, yet, when used habitually, never fail to 

 produce debility of that organ, and in this manner impede digestion. 

 Salt, pepper, and vinegar, are exceptions, and are not obnoxious to 

 this charge when used in moderation. They both assist digestion, 

 vinegar, by rendering muscular substance more tender and both, 

 by producing a fluid having some analogy to the gastric juice. 

 Spirituous, and probably all artificial drinks, cider excepted, impede 

 more or less the digestive process ; some more so than others, but 

 none can claim exemption from the general charge. Even tea and 

 coffee, the common beverages of all classes of people, have a ten- 

 dency to debilitate the digestive organs. 



After a full meal, rest should be taken for at least an hour. 

 After that, moderate exercise rather aids digestion, but severe and 

 fatiguing exertion always impedes its performance. An experiment 

 was made by a medical" man on a couple of dogs of the same litter, 

 and of equal health. After giving them a good dinner of flesh, 

 one was taken out and hunted for four hours, while the other was 

 permitted to lie down and sleep. They were then both killed ; 

 the hunted dog had the meat in his stomach quite undigested, the 

 idle one had it quite gone. The lesson is a most instructive one. 



The intestines form a membranous tube nearly six times the 

 length of the body, about five-sixths of this length belonging to the 

 small intestines, and about one sixth to the large. The small intes- 

 tines are the canals in which the chyme is received from the sto- 

 mach ; and when digestion is completed, the large serve chiefly as 

 receptacles for the refuse which is to be expelled from the body. 



In the figure the small intestine is seen commencing from the 

 smaller or right extremity of the stomach, passing to the right side/ 

 where it lies close below the liver, and receives from it the gall 

 ducts ; then turning downward and to the left, where it receives the 

 ducts from the pancreas ; then twisting and forming a great number 

 of convolutions which lie chiefly in the middle of the belly, round 

 about the navel, and finally terminate in the large intestine in the 

 right side. The whole intestine is lined with a continuation of the 

 velvety membrane which lines the stomach, and which is constantly 

 moistened by a mucous secretion. The thickness of the gut is 

 formed of muscular fibres, arranged in two layers, the outer layer 

 being longitudinal, and the internal layer circular. The effect of 

 the gradual contraction of these fibres is to squeeze the food down- 

 ward ; and if the belly of an animal newly killed be opened, the 



