EPIDERMIC PRODUCTS 



257 



Its inferior surface is hoUowed out in the middle by an 

 excavation, which is known as the median lacuna. This 

 cavity separates the branches of the frog, which ter- 

 minate posteriorly by two swellings which are known as the 

 ■prominences of the frog, forming two rounded elevations 

 situated above the claws. These same branches unite in 

 front of the median lacuna to form the body of the frog. 

 This latter, in its anterior part, gradually narrows, and 

 terminates in a point which occupies the bottom of the 

 hollow limited laterally by the bars of the wall and the 

 posterior border of the sole. 



Between the lateral surfaces of the frog and the bars 

 are found two angular cavities — the lateral lacuncp,, or the 

 cofnmissures of the frog. 



Fig. ioi. — Third Phalanx of 

 THE Horse : Left Anterior 

 Limb, Inferior View. 



I, External border; 2, internal 

 border ; 3, semilunar crest ; 4, 4, 

 re-entrant processes. 



Fig. 102. — Third Phalanx of 

 the Horse: Left Posterior 

 Limb, Inferior View. 



I, External border ; 2, internal 

 border; 3, semilunar crest ; 4, 4, 

 re-entrant processes. 



As an indispensable complement to the study which we 

 have just made, it is necessary to add that the hoofs of the 

 fore-limbs and those of the hind ones present differences 

 of form which cannot be ignored — differences which we are 

 already able to conjecture by looking at the respective third 

 phalanges which terminate those limbs, and especially at 

 their inferior surfaces (Figs. loi, 102). 



The hoofs of the fore-limbs (see Fig. 100), viewed on their 

 plantar surface, are more rounded than those of the hind- 

 limbs (Fig. 103) — so that their external contour may be 

 compared to a semicircle — whilst the hind-hoofs, which are 



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