8 TRICHOLOGIA MAMMALIUM ; 
caloric; a very low specific gravity; no contractibility, and is of gradual and periodical 
decidence.* 
Tue most Important Division or Pite.—Pile is divided into hatr and wool. (See fig. 
2.) Hair and wool differ, one from the other, as follows :— 
Ist. In shape,—hair being either cylindrical, cylindroidal, oval or ovoidal,—while wool 
is eccentrically elliptical. 
2d. In uniformity of shape of the same filament,—hair being generally the same shape 
throughout the filament,—while wool is less uniform in this particular. 
3d. In the formation of the cortex, the scales of which upon hazr are less numerous, less 
pointed, and more depressed,—while those upon ool are more numerous, more pointed, 
and less depressed. 
4th. In direction,—hazr being either straight, flowing, or curled,—while mool is crisped 
and frizzled, and sometimes spirally curled. (See Frontispiece.) 
* EXrLaNavion or TeRMS.—Eyery part of the above description will, in its turn, in the succeeding pages, become a subject 
of discussion; wherefore, all that is here required, is to explain, briefly, some of the terms. 
“Filamentus,” from (filamentum,) a fine slender thread; used synonymously with “fibre,” (fibra;) but we prefer the 
use of the word filamentous, reserving the words fibre and fibril, (a small fibre,) for the description of the intermediate sub- 
stance of the shaft. 
“Appendage.” Something that, being less than the principal, is annexed or added to it. 
“Dermis.” The cutaneous system is divided into an external, including the dermis and epidermis, and an internal or 
mucous membrane. Pile belongs to the dermis, hut sometimes penetrates to the adipose tissue. 
We have not made an extensive microscopic examination of the skin; and will therefore content ourselves with giving the 
description of it found in the books. 
It is represented as consisting of four principal portions, viz:— 
Ist. The epidermis, or cuticle, which forms the outermost layer. This is of membranous structure, and is devoid of vessels 
and nerves, and of course insensible. It is pierced with minute oblique holes, for the passage of hairs, and for the orifices 
of exhalent and absorbent vessels. The cuticle exfoliates, in the form of scales, from the head, and also from the body after 
certain cutaneous discases. 
2d. The rete mucosum, the appareil pigmental of Flourens, (see Anat. Gen’l. de la Peau, &e., p. 34,) of the eolored race. 
Some are of opinion that in the white race this is entirely wanting; others suppose it exists, but is of a red color. 
3d. The corpus papillare. It consists of a collection of small papilla, formed by the extremities of nerves and vessels 
passing the corium which is beneath. Flourens considers these papille as prolongations of the true skin, and not asa 
separate layer. 
4th, and lastly, comes the derma, corium, cutis-vera, or true skin; in which, principally, pile is set. 
Beneath all these is the adipose tissue. 
“Mammalia.” We confine pile to this, notwithstanding the teachings of some physiologists that it is extended to other 
classes of animals, and even to vegetables. ‘Quadrupedia corpus pilosum.”—(Lin.) “The bodies of all quadruped animals 
ure covered with hair.”—(Goldsmith.) ‘Les mamiferes sont les sewd animaux dont le corps est couvert de poil.”’—(Hlem. de 
Zoo. 282.,) &e. 
“Follicle,” the sac, in which the button of the hair is generally found, is most commonly, but improperly, called the 
“yoot,” whieh tends to mislead by suggesting a too intimate relation to a plant. We call at the ‘‘ Follicle.” 
The word “follicle” is generally applied, in anatomy, to excretory organs; but there is nothing in its derivation or termi- 
nology to prevent us from using it in the sense here notified. Follicle, from the Latin ‘folliculus,” (which is a diminutive 
of “follis,”’ a bag, purse or script,) is a small hag, purse or script, only, without limiting the use to which it is applied; and 
in Botany, where it has been introduced, means, ‘‘a seed vessel, husk, or cover. It is so used by the French, also, by whom 
“follicle” is defined, in Botany, to be ‘‘l’envelope membraneuse, dans la quelle sont contenue les graines des plantes.” We 
therefore use the word follicle to designate the little sac in which the posterior termination of the shaft, with its button, is 
contained, when the pile is perfect and has come to maturity. 
““Insensible.” Possessing no feeling, yet not deprived of all the properties of life. 
