62 THE veterinary science 



burying ground of the red corpuscles. It is well supplied 

 with blood vessels and nerves and weighs in the average 

 horse from two to four pounds. 



III. — MEMBRANES OE THE BODY. 



Membranes of the body are spoken of as Mucous or 

 Serous. 



11. Mucous Membrane. — All open cavities of the body 

 are lined with mucous membranes, as, for example, the lining 

 all through the alimentary canal of the digestive organs. The 

 lining of the respiratory or breathing organs is of mucous 

 membrane, as also is that of the urinary and genital organs 

 or those which produce the young animals. 



12. Serous Membranes form the lining of closed cavities, 

 that is air-tight cavities, those that do not communicate at all 



.with the air. The peritoneum, situated between the bowels 

 and the wall of the abdomen, is an important example. The 

 pleura which lines the chest cavity and the lungs is another. 

 A third, less important, may be found in the brain. 



Serous membrane is always made up of two coats, the 

 inner being attached to the organs contained in the cavity 

 and the outer closely lining the inside of the cavity in which 

 it is found. An oily fluid is always secreted from the inner 

 side of these membranes. This fluid lubricates the surfaces, 

 and thus prevents soreness or inflammation that would other- 

 wise result from the friction caused by the moving of one 

 coat on the other. These membranes are very important and 

 should be very carefully noted, as they sometimes become 

 chilled and inflamed and thus the source of further inflam- 

 mation. Inflammation of the pleura is called pleurisy. In- 

 flammation of the peritoneum, the membrane connected with 

 the bowels, is called peritonitis. It is a very dangerous dis- 

 ease, much more so than pleurisy. 



IV. THE PROCESS OF DIGESTION. 



The food is taken into the mouth by the lips and front 

 teeth. Here it is masticated or chewed by the teeth with 

 the assistance of the tongue, at the same time receiving from 

 the salivary glands a digestive fluid called the saliva which 

 softens and prepares it for digestion. After being thoroughly 

 ground up and mixed with saliva it is rolled into a ball at 

 the back part of the tongue, where by the action of the 



