SOLIPEDA. 



737 



liquely, upon the left side of the stomach ; its 

 base pointing upwards and backwards, and its 

 apex downwards and forwards; it is about 

 9 inches long, 4 inches broad at its widest 

 part, and three-quarters of an inch in thick- 

 ness. Its weight is about twelve ounces. 



The pancreas is of an irregular shape, ap- 

 pearing to be made up of three branches the 

 shortest of which terminates at the duodenum ; 

 of the other two, one extends beneath the 

 right, and the other reaches as far as the left 

 kidney: these three branches form, by their 

 union, a flattened mass, about half an inch in 

 thickness, which may be called the body of 

 the pancreas. There is nothing remarkable 

 in the arrangement of its excretory duct. 



CIRCULATORY APPARATUS. The struc- 

 ture of the heart and the general arrangement 

 of the arterial and venous systems offer no pecu- 

 liarities worthy of notice. 



STRUCTURE OF THE HORSE'S FOOT. The 

 mechanical structure of the foot of the horse 

 demands to be considered at length, for in what- 

 ever point of view this part of their economy 

 is regarded, either as a simple instrument of 

 progression,, or a curious piece of anatomy, it 

 will be found equally deserving the study of 

 the physiologist arid of the veterinarian. Nu- 

 merous writers have accordingly devoted their 

 attention to this subject, both on the conti- 

 nent and in our own country ; but their^le- 

 scriptions are, unfortunately, so mixed up 

 with terms of farriery and stable jargon, that 

 the anatomist finds considerable difficulty 

 in deciphering their elaborate disquisitions. 

 Among the most philosophical English treatises 

 are those of Professor Coleman and Mr. Bracy 

 Clark, to both of whom we shall be indebted 

 for many of the following observations. 



Horny hoof. The whole exterior conical 

 covering of the horse's foot, called in tech- 

 nical language the " wall of the hoof," is 

 formed of a dense horny substance, which in 

 shape resembles a hollow cone obliquely 

 truncated at its upper part, so that the hoof 

 is deepest or highest in front of the foot, 

 diminishing in this respect as it recedes back- 

 wards towards the " quarters ; " it then loses, 

 to a considerable extent, its conical shape, 

 and becomes nearly upright, especially on the 

 inside or inner quarter, still growing narrower 

 or lower to the posterior extremity of the 

 foot, where, at first sight, it appears to termi- 

 nate by mixing with the substance of the 

 "frog," hereafter to be described, and with 

 the integuments of the posterior region of the 

 foot : instead of terminating in this manner, 

 however, a more accurate examination shows 

 it to be suddenly inflected inwards, pursuing 

 its course towards the centre of the foot, 

 where, diminishing gradually in depth, it is 

 finally lost, becoming mixed up with the 

 " sole," near the point of the frog, thus form- 

 ing a distinct and remarkable internal wall that 

 supports the under parts of the foot, and at 

 the same time protects, by its bold projection, 

 the sole and the frog from an undue degree of 

 pressure and contusion against the ground. 



The parts thus formed by a continuation of 



the wall of the hoof beneath the foot, are 

 called the " bars of the foot" and are fre- 

 quently described with, and taken for, part of 

 the "sole." The direction of this sloping 

 floor serves to throw all superincumbent pres- 

 sure outwards towards the sides of the foot, 

 and at the same time leaves a triangular space, 

 posteriorly, for the insertion of the frog 

 (fig. 513.), which it likewise protects from 

 injury. 



Fig. 513. 



Structure of the hoof of the Horse. 



1, the sole ; 2, section of the horny hoof; 3, upper 

 surface of the frog ; 4, 4, the horny heels ; 5, Bars of 

 the foot; 6, walls of the hoof; 7, 8, 9, 10, 11, boun- 

 daries of the vaulted space, ,in which the frog is 

 lodged ; 12, 12, the sensitive foot. 



The wall thus constructed appears to form 

 the basis of the mechanism of the hoof, to 

 which all the other parts are subordinate, and, 

 if so understood, will much facilitate our views 

 of the nature and economy of its structure. 

 Its inner surface is every where lined, as it 

 were, with numerous elastic lamella? that pro- 

 ject internally, and arranged in parallel lines, 

 proceeding downwards perpendicularly to- 

 wards the front of the foot (fig. 514, 3.) : these 

 horny laminae are, at least, five hundred in 

 number, and afford, from the aggregate surface 

 that they present, a very extensive superficies 

 for the attachment of an equal number of 

 similar processes, derived from the vascular 

 surface that covers the coffin bone, with which 

 they interdigitate in such a way that the pres- 

 sure to which the foot is subjected, which if 

 concentrated upon a small surface would in- 



3 B 



