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CHAPTER III. 

 DISEASES OF THE DIGESTIVE SYSTEM. 



PROPERLY speaking, the first portion of the digestive canal is the mouth. As, however, the 

 diseases of this region are described in another chapter, we shall for the present pass over 

 this, merely mentioning the fact that mastication can hardly be said to be performed by the 

 dog, who belongs by nature to the carnivorous animals. In mankind the due mingling of 

 the food with the saliva is of the greatest importance in the economy of digestion. In the 

 dog it is equally or almost equally so, but the food does not require to stop so long in the 

 mouth, owing to the greater abundance of the salivary juices. 



Now we shall be in a much better position to understand the diseases of the digestive 

 canal if we first and foremost give our attention for a moment to a short description of the 

 anatomical and physiological construction of the nutritive canal, and to the theory of digestion. 

 Such description can hardly fail to be of interest to the majority of readers. 



The first portion, then, of the canal to be considered, is that which, beginning at the 

 mouth, ends at the upper or cardiac opening of the stomach. It is. called the oesophagus or 

 gullet; it lies directly behind the larynx and trachea or windpipe. The oesophagus is some- 

 what funnel-shaped ; that is, it is very wide at the top, the upper portion being termed the 

 pharynx. This is divided from the mouth by a movable curtain called the veil of the palate. 

 In the dog the oesophagus is all along its course very dilatable, hence the immense masses of 

 flesh and pieces of bones which the animal can swallow. 



From the lips all the way to the anus the alimentary canal is lined by what is called 

 mucous membrane. This is, in other words, a sort of inner skin, and while the outer or true 

 skin secretes perspiration and sebaceous matter, this membrane secretes mucus. 



This mucus keeps the membrane moist, and lubricates the mouth and gullet for the 

 passage of food. In the mouth, nose, cheeks, palate, Sec., this membrane is a plain secreting 

 lining, it does not absorb to any appreciable extent. In those portions of the canal where 

 it not only secretes but absorbs, we find it no longer a plain lining membrane, but corrugated, 

 to give it a larger surface in less space. 



In some parts of the mucous membrane, as the stomach for example, we find that not 

 only is the surface studded with villi, which give it the appearance of the pile of velvet, but 

 also with little pits or holes, the openings of numerous culs de sac, or minute mucous pouches 

 called follicles. Now, each follicle and villus is supplied with its own little artery, vein, and 

 nervelet, and the villi absorb while the follicles or pouches secrete. 



In the animal body immensely large surfaces are required for the vast amount of fluids 

 and juices that have to be secreted, so that Nature is in a manner cramped for room. Hence 

 the economy of that wonderful multum in parvo, a secreting gland, the mechanism of which is 

 not only very beautiful but very simple. If it were not for those little secreting pits or follicles 

 in the stomach, the surface of that organ would have to be of immense size. A follicle, then, 

 a pit or depression, is the very simplest form of secreting gland imaginable. A large number of 

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