INTEENAL ANATOMY OF HORSE. 297 



Internal Anatomy. 



The skin, or outer covering of the muscles, skeleton, and 

 organs, also represents the organ of " touch " — certain areas, 

 such as the lips and limbs, being especially adapted to this 

 sense. The skin is composed of two layers — the outer the 

 epidermis, the inner the dei-mis. The epidermis is the thin 

 layer covering the face of the derma, and is formed of flat cells, 

 which are continually being deposited and worn off by friction. 

 The derma forms the chief thickness of the membrane, its inner 

 face adhering closely to the subjacent parts by the pannictilus 

 adiposus, a ceUulo-adipose substance. The external face is per- 

 forated by openings for the hairs and exits of the sudoriporous 

 and sebaceous glands. The nerves end in the upper part of this 

 layer in little papillarlike projections. 



The skin of the horse having been removed, there is 

 found underneath a thick coating — thin, however, in places — 

 of a red, more or less striped appearance, which can easily be 

 divided up into different detached areas. These are the muscles, 

 the so-called flesh which is attached to the bones, forming not 

 only a covering for the more delicate internal parts, but also a 

 very complicated mechanical apparatus for the movement of the 

 animal, &c. The individual groups of muscles on examination 

 will be seen to be composed of a number of bundles of fibres, each 

 of which is endowed with the power of contraction. During 

 this contraction a muscle becomes shorter and stouter : on the 

 contraction ceasing the muscle regains its normal length by 

 an elastic recoil, muscle being also elastic in nature. Many 

 muscles terminate in tendons/ these latter, and the muscles 

 themselves, are attached at each end to a bone. For such a 

 purpose are the roughened ends of the femur and the side 

 swelling of the third trochanter formed. When the muscle con- 

 tracts, one end to which the muscle or tendon is attached must 

 give way and be pulled towards the other, and thus the move- 



