CLASSIFICATION OF ANIMAL PREPARATIONS. 435 



injected, should be selected, as In them the mode of growth of 

 the young whiskers, their copious supply of blood-vessels and 

 nerves, and various other points of interest, may be observed. 

 In fishes, the only parts of the skin generally prepared as 

 microscopic objects are those more or less covered with scales, 

 hence may be seen, in various lists of preparations, the skin of 

 the sole and shark ; in reptiles, also, we have the skin of the 

 snake, boa, and some lizards, whilst in birds, except when 

 injected, the skin offers but few points worthy of examination 

 besides the feathers. In man and the higher mammalia, the 

 complicated apparatus of glands and papillse are best examined 

 by vertical sections ; but in order to render the skin sufficiently 

 firm for the purpose, it should have been previously hardened 

 in a saturated solution of carbonate of potash, or in strong 

 nitric acid. The hair follicles and sebaceous glands are 

 easily shown, but to display the sudoriferous glands is no easy 

 matter, as rarely will a specimen of skin be found that will 

 exhibit them and their spiral duct in the whole of its course 

 through the dermal and epidermal layers ; it is by far better 

 to try the skins of a number of persons, and select the one 

 that shows them the best, than to waste time by cutting 

 a series of slices from any one specimen. The papiUse are 

 best shown in the extremities of the fingers and toes, when 

 injected; the cuticle which invests them should also be 

 mounted up as an object with its attached or papUlary surface 

 uppermost, as in this the grooves for their lodgment, together 

 with the openings of the sudoriferous glands, can be well seen. 

 The following list will include a few of the most important 

 specimens : — 



Vertical Sections. Free Surface. 



Ass (corn), Man (axilla), Man (face), 



Bear (sole of foot), Negro, — (lips), 



Cat (upper lip). Pig, — (tips of finger). 



Dog (upper Up), — (snout), — (cuticle of finger). 



Kitten (upper lip), — (ungual phalanx), — (back of finger), 



Man (sole of foot). Porpoise (with cuticle), — (nose), 



— (palm of hand), (without cuticle). Newt, 



— (scalp). Tiger (upper lip), (cuticle), 



— (face), (whisker injected). Porpoise. 



28* 



