92 PHILOSOPHY OF ZOOLOGY. 



Hair is found on all the mammalia, whales not except cd ; 

 differing greatly, however, in quantity, according to the 

 sj>ecics, but always most abundant on the parts most ex- 

 posed, and on those animals which inhabit cold countries. 

 It is found, along with feathers, on different parts of the 

 body of birds, chiefly, however, on the head and neck. It 

 is absent in the reptiles, fishes, and mollusca ; but it may 

 be observed on many annulose animals, and even zoophytes, 

 in which it acts the part of an organ of motion. 



Of all the substances consisting of animal matter, hair is 

 the most permanent, resisting putrefaction for a great length 

 of time. According to the experiments of HATCHETT, it 

 consists of gelatine and coagulated albumen. VAUO.UELIX 

 detected two kinds of oil ; one of which was found to vary 

 in colour, according to the colour of the hair from which it 

 was extracted ; black hair yielding a black oil ; the other 

 always white, without regard to the original colour of the 

 hair. Hair likewise contains iron, oxide of manganese, 

 phosphate and carbonate of lime, silica, and sulphur, 



2. Feathers. As nearly related to hairs in the animal 

 economy, in regard to situation, composition, and purpose, 

 we may here take notice of the plumage of birds. 



Feathers may be considered as consisting of the following 

 parts : the quill, the shaft, and the web. 



The quill takes its rise, like the hair, in the cellular 

 membrane, and passes through a tubular opening in the 

 other layers of the skin, which generally exhibit a duplica- 

 ture at its base, forming a short sheath. The edges and 

 outer side of the distal part of the quill unite with the 

 proximal end of the shaft, leaving a small opening in the 

 middle of the inner side. 



The sliaft consists of a cuticular layer of matter similar to 

 the substance of the quill ; and a central portion, of a while 

 colour ; and with a texture like cork. The outer side is in 



