34 PHYSIOLOGY. 



The lymphatics carry a fluid called lymph, which is a 

 limpid fluid, and found in all parts of the body. They take 

 up substances that are applied to their mouths ; thus the 

 moisture within the abdomen, and other cavities, or poisons 

 rubbed on the hide, are taken into the system. The absorb- 

 ents also assist in this process, the latter taking up all the 

 useless matter, and conveying it into the blood, that it may 

 be thrown off by the skin and kidneys, in the form of urine 

 and perspiration. 



The external surface pf the intestines consists of perito- 

 neum, a membrane from which the viscera of the abdomen 

 derive their external coat. The peritoneum forms also a kind 

 of sac, in which they are enclosed. The first portion of 

 intestine-duodenum is about twenty inches in length. The 

 next is named jejunum ; the third illium : this terminates in 

 the caecum, or first of the large intestines : here there is a 

 looseness of the internal coat, which allows it to be formed 

 into folds, and effectually prevents the return of excrement 

 into the small intestines. The second of the large intestines 

 is named colon. It is small at its commencement, but soon 

 after enlarges into a very capacious canal, which, when it has 

 passed nearly around the abdomen, again forms a second, but 

 slight contraction ; after which it again enlarges, when, less- 

 ening a third time, it terminates in the rectum. The anus, 

 or fundament, is the termination of the rectum, and is shut 

 by a circular muscle, termed sphincter, which surrounds the 

 end of the gut. 



Circulation of the Blood. — Having given the reader some 

 idea of the manner in which the blood is made, we will now 

 consider its properties, and explain how it is propelled and 

 distributed to every part of the animal. 



The appearance of blood is familiar to most persons. We 

 have already stated that it contains the elements for building 

 up and nourishing the whole animal structure. On examin- 

 ing blood with a microscope, it is found full of little red 

 globules, which vary in their size and shape in different ani- 

 mals, and are more numerous in warm than in cold blooded 



