92 ANIMAL PARASITES AND MESSMATES. 



dings of the stomach ; it is from them that we can appre- 

 ciate the bill of fare of each. This study of the food will 

 one day excite much interest, not only in a scientific 

 paint of view, but also with reference to fishing as an 

 occupation. 



There are some animals which are infested at every 

 period of their life, and at every season ; others in far 

 greater number only during their youth, and they gather 

 in at the commencement of their life the harvest for the 

 rest of their days. The greater part of . parasites, espe- 

 cially of fish, are introduced with the first nourishment. 

 As soon as they issue from the egg, young rays, like 

 young turbots, are already stuffed with worms which 

 afterward obstruct the digestive organs. The stomach of 

 each of these fishes is like a filter which allows every 

 thing which is food to pass, but detains on its passage 

 and without any change all that is living. When we 

 examine the stomach and observe the food in its different 

 degrees of digestion, we see distinctly the worms coming 

 out of their holes, wallowing in that which physiologists 

 call chyle, and choosing afterwards at their convenience 

 the place where they may completely develop themselves. 

 At the end of a few days, the fish may have swallowed an 

 innumerable quantity of small animals, and if each of 

 them introduces some worms, we can easily understand in 

 how short a time the intestine becomes literally filled. 



There is no organ which is sheltered from the. in- 

 vasion of parasites : neither the brain, the ear, the eye, 

 the heart, the blood, the lungs, the spinal marrow, the 

 nerves, the muscles, or even the bones. Cysticerci have 

 been found in the interior of the lobes of the brain, in 

 the eye-ball, in the heart, and in the substance of the 



