54 PHYSIOLOGY OF THE HUMAN BODY. 
knee, the muscles that straighten the knee-joint, proceed from the front 
of the pelvis and from the femur itself, forming the fleshy mass in front of 
the thigh. 
The most important muscle of iu foot is that which forms the calf 
of the leg (A, fig. 50). It is of immense strength, because in raising 
the heel it has to raise the weight of 
the whole body. It is attached above 
to the bones of she thigh and leg, 
and is inserted by the tendon of 
Achilles, as it is called (a), to the heel- | 
bone. Another muscle, B, is attached 
to the tibia, and inserted in one of the 
. bones of the arch of the foot; and a 
‘third is attached to the fibula, and 
inserted in the outer metatarsal bone. 
These two last being inserted into -the 
outer and the inner edges of the instep, 
turn round the outer and inner ankle 
respectively. The raising of the toes, 
the turning of the foot outward, and the straightening of the sole, are 
effected by other two muscles (F, fig. 50, and a cane one on the other 
side), the tendons of which pass down in front of the inner and outer 
sides of the ankle, and are inserted in the inner and outer edges of the 
instep respectively. 

‘The Skin, Hair, &. 
THe SKIN consists of two layers, the true skin and the scarf-skin ; 
the former being called the dermis} or cutis,” and the latter the epidermis? 
or cuticle The dermis forms the thick layer of the skin, and is a 
strong, supple, elastic membrane, formed of a compact kind of tissue, 
which, in its ordinary form, has a spongy appearance, being full of little 
cells. This tissue is dennpoded of two elements—a yellow or elastic sub- 
stance, and a white or inelastic, tough substance ; and these substances 
are arranged in various proportions, acouilidly to ihe nature of the cover- 
ing that is wanted at a particular place. The cutis also: varies as to 
ee according to the amount of resistance or of protection required 
for the part covered; thus, on the sole of the foot, the cutis is very thick, 
‘and is composed principally of the tough white substance. On the outer 
surface of the cutis are a number of small flexible elevations, called 
"Hg papille ® or pimples, which will be mentioned again in treating of the 
1 From Greek derma, skin. 2 Latin, ‘skin.’ 
3 From Greek epi, upon, derma, skin. 4 From Latin cuticula, diminutive of cwtes, skin. 
5 Latin, diminutive of papule, pimples. 
