DISEASES OF THE DIGESTIVE ORGANS. 217 



is not the case with the salivary glands and their products. The 

 pnncreatic juice may, like every other secretion, be found to con- 

 tain adventitious substances that have accidentally entered the 

 blood. Thus, iodide of potassium may be eliminated from the 

 system by the pancreas. It is not so with every salt, the prussiate 

 of pot-ash, for example, never being seen in the pancreatic juice. 



The pancreatic secretion is formed during infra-uterine life, bur 

 we are at a loss to account for its uses there. It is difficult to de- 

 termine what nervous influences affects its production. A dose of 

 ether excites it, and pressure on the abdominal viscera likewise 

 tends to its increase ; the efforts of vomiting stop it." 



Worms or Parasites which infest the Intestinal Canal. 



There are various forms of parasites which infest the alimentary 

 canal of horses and cattle which, no doubt, are the cause of some 

 annoyance to the infested ; but really they are not, at all times, so 

 injurious as some writers make them out to be. They are rarelv 

 if ever found in the intestines of healthy animals, and their pres- 

 ence is generally due to a deranged condition of the digestive 

 organs. They very frequently originate spontaneously. 



" Certain independent organisms, both vegetable and animal, 

 are found in the body. The vegetable growths are all microscopic, 

 and belong to the lowest order of plants, the algaa and fungi. 

 They are never met with except upon cutaneous or mucous sur- 

 faces, nor while these surfaces remain healthy, usually. A secre- 

 tion of fibrine or mucus, undergoing decomposition, forms the soil 

 in which they grow. In some cases, they are believed to be the 

 media of contagion. 



Animal parasites are very numerous. Many of them are in- 

 fusorial. Many belong to the class of insects and mites, as fleas, 

 lice, bugs, and the acari, of which the most important one is the 

 itch-mite. A class of higher consequence comprises several sort 9 

 of worms. Those which infest the intestinal canal are extremely 

 common, and are the oxguris vermicularis, or thread-worm, which 

 inhabits the rectum ; the trichocephalus dispar, or long thread- 

 worm, which is found in the large intestine, and especially in the 

 caecum ; the ascares lumbricoedes, or round worm, whose ordinary 

 residence is the small intestine; the tape-worm, or taenia, which 

 ulso affects the same part. The kidney is occasionally the seat of 



