922 TEE SENSORY APPARATUSES. 



(the fifth or thumb not beiug sufficiently developed to reach the ground), and a large central 

 one, ciicumBcribed in front by the others. This arrangement diffuses the pressure caused 

 by the weight of the lx)dy (and, doubtless, ameliorates the coucussioa arising from the 

 exertions these animals uiake, as well as ensures their footsteps being noiseless when 

 approaching their prey). 



In the Cat, the claws are very sharp and retractile ; being capable of erection and depression 

 in tiie interdigital spaces, by means of a small yellow elastic ligament passing from the second 

 to the third phalanx. This animal's claws constitute its most powerful weapon of attack and 

 defence. 



In the Rabbit, the claws enable it to burrow in the ground : and the Dog can also employ 

 them in this manner. 



4. The Frontal Horns. 



These are conical horny sheaths, more or less large and curve 1, and annulated transversely ; 

 they are formed by concentric layers of epithelial cells and s .me pigment-corpuscles. The 

 horns grow in the same manner as the wall of the Horse's hoof. The keratoijenous membrane 

 covering the core arising from the frontal bone, like that covering the last phalanx of the 

 Horse, has a papillary coronary portion at the base, and a laminer portion lor the remainder 

 of its extent. The coronary base forms the matrix for the horn. 



(The length, direction, and general form of the liorns varies in Ruminants, not only with 

 regard to species, age, and race, but also sex. The Bull, in the bovine species, generally has 

 short, thick, powerful horns; the Cow, long and slender ones; and the Ox, large, long, and 

 strong ones. Some breeds have no horns at all. It is the same with the Goat species, 

 though generally the horns in these are long, flattened, and curved backwards and downwards. 

 "With the Bam, the horns are sometimes immense and very powerful, being of a spiral form. 

 They are usually less, or altogether absent, in the Ewe. In the Bovine species, the transverse 

 rings on the horns serve to indicate the age, the first appearing afier two years.) 



5. The Chestnuts. 



This name is given to a little horny (oval or round) plate found, in the Horse, on the inner 

 face of the forearm — in tiie lower third of the region, and at the upper extremity of the inner 

 face of the metatarsal bone. It is composed of a mass of epithelial cells, arranged in tubes 

 like the horn of the hoof. In Solipeds, the chestnut is the repretentative of the thumb.' 

 That on the posterior limbs is absent in the Ass ; in the Mule it is very small. 



(In fine-bred Horses, this horny production is much less developed than in the coarser 

 breeds. It is always smaller in the hind limbs. 



6. The Ergots. 



In the hind and fore legs, we also find a similar, but smaller corneous mass, growing from 

 the skin of the fetlock, and named the ergot. Like the chestnut, it bears the same relative 

 deTelopment in fine and coarse-bred horses.) 



CHAPTER II. 



APPARATUS OF TASTE. 



The sense of taste permits the appreciation of savours, or the sapid properties of 

 bodies. 



Two nerves — the chorda tympani and the hngual branch of the ninth pair — 

 appear at present to be the only sensory filaments endowed with the exercise of 

 this function. They ramify in the lingual mucous membrane, which is thus 

 made the organ of taste. (Three nerves are usually mentioned : 1. The glosso- 



(' This is very doubtful, particularly for any member of the class Ungulata ; and from the 

 fact that in the Rhinoceros and Tapir the second digit is perfectly developed, these epidermic 

 appendages would be most probably larger in them than in the Horse, if they represented the 

 pollex and hallux; however, they are altogether absent. Besides, in tlie anterior limb of 

 the Horse and Ass they are above the carpus.) 



