62 A HALF-HOUR WITH THE 



The study of the uses of the epidermal ap- 

 pendages is one full of interest, as in no one 

 set of structures do we find a greater variety of 

 adaptations of a common plan to the wants of the 

 creatures in which they are found. The feathers 

 of birds belong to the same type of structure as 

 the hairs of animals. If the pinnae of a common 

 goose-quill, used for a pen, are examined, the 

 pinnules will be found to be covered with minute 

 hooks (Fig. 187, PI. 7). These hooks on the upper 

 surface are so arranged that they catch the nearly 

 plain and slightly toothed pinnules on the lower 

 side. 



The clown from the feathers of the swan, with 

 which pillows and beds are stuffed, is also a beau- 

 tiful object, and its microscopic structure (Fig. 188, 

 PL 7) will at once reveal the cause of its lightness, 

 softness, and warmth. 



Amongst the creatures which domesticate with 

 us are certain insects which are more frequently 

 discovered than acknowledged. However dis- 

 agreeable their presence may be, they become 

 interesting objects for microscopic investigation, 

 and are not less calculated to excite our admira- 

 tion than creatures more ceremoniously treated. 

 We first call attention to the flea. This beautiful 

 insect belongs to a large family, each species of 

 which has its peculiar habitat in the epidermal 

 appendages of some of the higher animals. The 

 head of the human flea may be taken as the type 

 of the family (Fig. 189, PL 7). It is furnished with 

 antennae, mandibles, and a pair of lancet-shaped 

 jaws, with which it makes little wounds in the 

 skin ; and into which it pours the irritating secre- 

 tion which renders its bite a source of annoyance. 

 Its eye, large hind legs, and ornamental saddle on 

 its back, are all deserving of attention. 



