ANATOMY AND PHYSIOLOGY OF THE HORSE. 



15 



PHYSIOLOGY OF THE SKIN. 



The skin is higlily sensitive ; yet those 

 persons who are in the habit of making free 

 use of the whip scarcely ever realize the 

 fact. The author has an impression that 

 the skin of a horse is more sensitive than 

 that of man ; for example, let a small quan- 

 tity of turpentine be applied to a horse's 

 back, — very soon he evinces signs of pain, 

 which cannot be elicited when a man be- 

 comes the subject of the same experiment. 

 Every horse-owner, also, must have noticed 

 the uneasiness a horse manifests when a 

 common fly, or gad-fly, alights on him ; and 

 in a variety of other ways the highly sensi- 

 tive state of a horse's skin admits of dem- 

 onstration. 



The skin is one of the principal emunc- 

 tories of the body, from the surface of which 

 passes off a large quantity of morbid fluid 

 in the form of perspiration, sensible or in- 

 sensible, as the case may be. The skin is 

 the great external outlet; and, should the 

 kidneys or any other organ fail to play their 

 part in eliminating useless fluids, the skin 

 opens its flood-gates, and thus purifies the 

 body. The amount of fluid exhaled from 

 the external surface has been the subject of 

 some very interesting experiments, and the 

 results are truly astonishing. 



OF THE CELLULAR MEMBRANE BENEATH THE 



SKIN. 



This tissue abounds in almost every part 

 of the body; thus, says Carpenter, "it binds 

 together the ultimate fibres of the muscles 

 into minute fasciculi, unites this fasciculi 

 into larger ones, these again into still larger, 

 wMch are obvious to the eye, and these into 

 the entire muscle ; and also forms the mem- 

 branous divisions between distinct muscles. 

 In like manner it unites the elements of 

 nerves, glands, etc., binds together the fat- 

 cells into minute masses, these into larger 

 ones, and so on ; and in this manner pene- 

 trates and forms a considerable part of all 

 the softer tissues of the body. It also serves 

 as the bed in which blood-vessels, nerves, 

 and lymphatics may be carried into the 

 substance of the different organs." 



This tissue consists of a net-work of 

 minute fibres and bands, which are inter- 

 woven in every direction, so as to leave in- 

 numerable areola, or spaces, which commu- 

 nicate freely with one another. 



Of these fibres, some are of the yellow or 

 elastic land, but the majority are composed 

 of the white fibrous tissue ; and, as in the 

 other form of elementary structure, they 

 frequently present the form of broad flat- 

 tened bands, or membranous shreds, in 

 which no distinct fibrous arrangement is 

 visible. The proportion of the two forms 

 varies, according to the amount of elasticity 

 or simple resisting power which the en- 

 dowments of the part require. The inter- 

 stices or areolae are filled, during life, with 

 a fluid which resembles very dilute serum 

 of the blood ; consisting chiefly of water, but 

 containing a sensible quantity of common 

 salt and albumen. It is the undue accumu- 

 lation of this fluid wliich constitutes drop- 

 sical effusion, the influence of gravity upon 

 the seat of which, shows the free communi- 

 cation that exists among the interstices. 

 This freedom of eommunication is still 

 more shown, however, by the fact, that 

 either air or water may be made to pass, by 

 a moderate continued pressure, into almost 

 every part of the body containing cellular 

 or areolar tissue, although introduced only 

 at a single point. In this manner it is the 

 habit of butchers to inflate veal; and* 

 impostors have thus blown up the scalps 

 and faces of their children, in order to ex- 

 cite commiseration. The whole body has 

 been thus spontaneously distended with air 

 by emphysema in the lungs; the air having 

 escaped from the air-cells into the surround- 

 ing areolar tissue, and thence, by the con- 

 tinuity of tliis tissue with that of the body 

 in general at the root or apex of the lungs, 

 into the entire fabric. 



The structure of the serous and synovial 

 membranes is essentially the same as the 

 above. The true cellular membrane is 

 sometimes termed reticular, while that con- 

 taining fat is called adipose . 



