292 DISEASES OF POULTRY. 



plumage. When our domestic hens are castrated, or 

 rather, have part of the egg tube cut out, for the purpose 

 of fattening, the plumage undergoes a similar alteration, 

 so as to render it difficult to distinguish the birds from 

 capons. 



This change in the color of the plumage of birds, as 

 well as the hair of other animals, is attributed to the 

 influence of some peculiar coloring matter of the system. 

 That singular description of mammalia and birds, 

 usually known under the name of " albinos/' I think, 

 with propriety, may be classed among the diseases, as 

 their characteristics appear to arise from a deficiency of 

 the coloring principle common to the skin, hair or fea- 

 thers, and eyes. Thus, the skin generally has the hue 

 which its cellular and vascular contexture produces ; the 

 hair or feathers is produced to its simple organic ground 

 work ; and in the eyes, which are entirely destitute of 

 pigmentum, the color of the iris depends on the fine 

 vessels which are so numerous in its composition, and 

 that of the pupil, or the still greater number of capilli- 

 aries which almost entirely form the choroid membrane. 



The albino or leucoethiopic constitution occurs both in 

 wild and domestic animals as well as in the human sub- 

 ject. It is not only well known in the ferret, mouse, 

 rat, monkey, squirrel, hamster, Guinea pig, mole, opos- 

 sum, martin, weasel, fox, roe, rhinoceros, elephant, 

 badger, beaver, bear, camel, buffalo, blackbird, crow 

 and partridge, but in the horse, ass, sheep, pig, cow, dog, 

 cat, rabbit, Canary bird, peacock, and the common fowl. 

 In the mammalia and birds just enumerated, the nature 

 and characters of the deviation seem to be perfectly ana- 

 logous to those in the human albino. The pure white- 

 ness of their skin and other integuments, and the redness 

 of the irides and pu )ils mark the same deficiency of 

 coloring matter. 



