58 TRICILOLOGIA MAMMALIUM ; 
exerted, it flows or curls in the direction of one of these flattened sides, in exact proportion 
to the eccentricity of the ellipse. An eccentrically elliptical filament of pile, being still 
flatter, the spiral curl is the necessary consequence. 
Proofs.—Every one knows how easy it is to bend a spatula, (which is fibrous,) in the 
direction of either of its flattened surfaces, while his whole strength cannot make it bend 
in either of the contrary directions. Just so it is, (except in an inferior degree,) with a 
flattened hair ; a small degree of elastic force will cause it to flow towards one of its flat- 
tened sides, and a little more will make it curl in the same direction; but no stretching 
or shrinking force ever makes it flow or curl edgenise, or in the direction of its ellipse. 
From a piece of wood, (where the fibres acting conjointly preserve the whole mass 
straight,) plane a thin shaving, and it will curl. It is the same force that preserves a 
ratch-spring in a spiral curl, while an equal quantity of metal, in a cylindrical form, will 
be straight. Passa cylindrical hair between rollers, flattening it, and it will flow, curl or 
form spiral curls in proportion to the flattening. 
The Consequences.—'These laws being firmly established, we can judge of the direction 
of pile by its shape, and of the shape of pile by the direction.* We will recur to this sub- 
ject again directly. 
OF THE INCLINATION OF PILE or THE Heap.—By the inclination of pile we mean the 
angle which the filament forms with the tegument from which it proceeds. This inclina- 
tion does not depend upon the shape, nor upon the direction ; nor does the direction 
depend at all upon the inclination; but it is due entirely to the angle which the root of the 
pule bears to the skin of the animal in which it ts imbedded. 
The roots of cylindrical and oval pile have an acute angle of inclination; for which 
reason those hairs do not grow out of the epidermis at a right angle thereto, but incline in 
a determinate manner; while the roots of eccentrically elliptical pile lie in the dermis 
perpendicularly, and hence the filaments pierce the epidermis at right angles thereto. 
Of particular inclinations of Pile.—'Vhe foregoing description of the general inclination 
of pile of the head is governed by the following subordinate rules, viz: Ist. That of the 
anterior part of the cranium inclines obliquely in front, having a tendency to cover the 
forehead, and that of the posterior and inferior portions obliquely, transverse, so as to make 
the locks fall naturally along the posterior part of the neck; it is the same with the sides 
of the head, where the imclination carries this covering to the region of the ears. But 
these inclinations are, sometimes, partially artificially altered. Bichat ventured the 
opinion that these natural inclinations of the hair belong to the part of the bone which lies 
underneath ; but of this we see no proof. The skull of the negro and that of the white 
man, are composed of the same number of pieces. 
* Tt is true that sometimes the shrinking process of the two flattened sides alternate, when an exception, in the shape 
of the undulating hair is the consequence; but generally, if the shrinking force of the fibre on one flattened side of the 
filament, gains the ascendancy over that of the other side, a curl in that direction is permanent; for the more the former is 
eurved, the more force will be required for its recursion, and the more the latter is stretched, the less will be its power to 
return to its original condition. 
