34 



ANATOMY AND PHYSIOLOGY OF THE HORSE. 



Being in the hoofloss foot equally promi- 

 nent with the projecting edge of the coffin- 

 bone, one might be led to infer that the 

 horny frog should take the same line of 

 bearing with the crust. The frog, alto- 

 gether, is lodged in a capacious irregular 

 space, bounded superiorly by the tendo- 

 perforans and common skin, laterally by the 

 cartilages, and inferiorly by the horny frog : 

 with all which parts it has connections ; 

 besides being continuous with the sensitive 

 bars and sole, and at the heels with the 

 coronary substance. On its sides are two 

 shallow, ill-defined hollows, corresponding 

 to the commissures of the horny frog, into 

 which are received the horny prominences 

 opposed to them. 



" Structure. — Entering into the com- 

 position of this body we distinguish four 

 parts : An exterior or cuticular covering ; 

 a congeries or network of blood-vessels ; a 

 fibro-cartilaginous texture ; and an elastic 

 interstitial matter. 



" The exterior or cuticular covering in- 

 vests the prominent bulbous portion of the 

 frog, and also gives a lining to the cleft. 

 Superiorly, it is continuous with the skin 

 descending upon the heels ; anteriorly, with 

 the cuticular covering of the coronet ; infe- 

 riorly, with that of the sole. Numerous 

 villous processes sprout from its surface, 

 and enter the porosities in the interior of 

 the horny frog, taking a direction down- 

 ward and forward, the same as that in 

 which the fibres of the horn grow. 



" The vascular covering succeeds the 

 cuticular, lying immediately underneath it. 

 It consists of a network of blood-vessels, 

 principally veins, but which are not so 

 thickly set as upon the sole. 



" The fibro-cartilaginous case comes next. 

 We find it spread over those parts most 

 subjected to pressure, and to be, in many 

 places, one-fourth of an inch in thickness. 

 From its interior are sent' off numerous 

 processes, pervading the elastic matter of 

 the frog, forming so many septa intercross- 

 ing one another, and dividing it without any 

 notable regularity into many unequal com- 

 partments. In the posterior and bulbous 

 parts, the septa exist in greater numbers, 

 and are closer arranged than in the middle 

 parts. The fibres of this vaginal substance 

 run obliquely downward and forward, and 

 become intermixed around the borders with 

 those of the bars and sole. 



" The elastic interstitial matter^ however, 

 composes the bulk of the sensitive frog. 

 It consists of a pale yellowish soft sub- 

 stance, which has been mistaken for fat or 

 oil, and hence has been named ' the fatty 

 frog.' When cut deeply into, it exhibits a 

 granulated appearance, and the fibrous in- 

 tersecting chords become apparent, putting 

 on the ramous arrangement of a shrub or 

 tree. Altogether, the sensitive frog forms 

 a peculiar, spongy, elastic body, for which 

 we lack some more appropriate name." 



