OUTLINE OF THE STKUCTURE OF THE HORSE. 63 



vessels, which have their mouths upon its surface, and are 

 constantly taking up the nutritive extracts of the digested 

 food and conveying them into the blood. The point of the 

 finest needle could not be put down anywhere upon the 

 mucous surface on which these vessels are distributed with- 

 out resting upon one or more of these little mouths. From 

 the effects of severe ill-usage, as well as of certain diseases, 

 these absorbents sometimes cease to act. Should they remain 

 inactive, the horse, with his supply of nutrition thus cut off, 

 J 8 soon reduced to a famishing condition. 



Only two natural divisions are found in the alimentary 

 canal. These are the large and small intestines. Anatomists, 

 however, have divided each of these parts into three sections. 

 This subdivision is particularly arbitrary in regard to the 

 small intestines, between whose three sections it is impossible 

 to discover any defined boundary lines. Hence in "the cut 

 of these organs, which appears in Chapter XTTI, we have 

 not attempted to index the different portions of the small 

 bowels. Their continuous series of convolutions, however, 

 are represented very naturally and plainly at b b. 



The small intestines occupy rather more than two-thirds 

 of the whole length of the alimentary duct, being between 

 sixty and seventy feet in length. From their comparatively 

 small diameter, however, they will contain only a little more 

 than one-half as much as the large bowels. When fully ex- 

 panded, they will hold about eleven gallons ; the others about 

 nineteen. Adding to these amounts the three gallons which 

 represent the measure of the stomach, and we find that the 

 entire capacity of the digestive tube is the enormous aggre- 

 gate of thirty-three gallons. 



The three sections into which anatomists divide the small 

 intestines have received the names of the duodenum, jeju- 

 num, and ileum. 



Duodenum is a Latin word, signifying twelve. It is thus 

 applied because this part of the bowels in man is about 

 twelve inches long. In the horse, however, its length is 

 about twenty-two inches. It extends from the pyloric orifice 



