552 COMPARATIVE ^STHESIOLOGY. 



COMPARATIVE ^ESTHESIOLOGY. 

 RUMINANTIA. 



THE concha of the ear is widely opened, projects outwards, and is less mobile 

 than that of the horse ; the internal and middle ears present no feature worthy 

 of note, except that the handle of the malleus is more curved. The tapetum 

 lucidum of the eye is of a golden green colour, inclining to blue at the circum- 

 ference. In all the domesticated animals the gland of Harder occurs ; and in 

 other respects generally the eye of the ruminant resembles that of the 

 solipede. 



The hair on the tail of the ox, like that of the ass, is long only at the 

 extremity, where it forms a tuft. About the frontlet i.e., between the horns 

 the hair is thick and curly, but in a degree varying in different breeds. 

 The wool found on some of the smaller ruminants may be regarded as a 

 modification of hair. 



The horns, or weapons of offence, consist of a layer of horn tissue, developed 

 from the secretion of a vascular and nervous membrane which covers the 

 horn-core, and forms at its base a circular pad, becoming continuous with the 

 dermis. Both the membrane and the pad contain keratogenous tissue, hence 

 the tissue of horns, like the wall of the horse's hoof, is derived from two 

 sources. The portion of the horn surrounding the pad is known as the root, 

 that covering the core the body, while the part projecting beyond the core is 

 the point. A number of rings appear, surrounding the horn just above its 

 root, which are rather unreliable indications of the age of the animal. In 

 shape horns vary much ; in the bovidae, the typical form is crescentic, with 

 the convexity turned more or less downwards and outwards ; in the ovidae, 

 where developed horns are less general, they are usually curved spirally, some- 

 times assuming a very graceful curve, the first bend being with the convexity 

 outwards and forwards ; in the goat they are closer together, and more 

 perpendicular, being slightly curved, with the convexity inwards ; all these 

 forms are subject to great variation, some species of ruminants, as the 

 camelida3, being altogether without horns, while in others their development 

 is enormous. 



Animals possessing horns of the above type are classed as cavicornia, or 

 hollow-horned. The horns of deer (antlers) differ from these, in being formed 

 of solid bone, in having branches, and being deciduous, falling off every year 

 to be replaced by new ones. 



The hoof is, of course, divided into two parts, one for each digit, each part 

 resembling in shape the distal phalanx. Their general structure resembles 

 that of the horse's hoof, but the frog is little developed. A small horny 

 projection appears on each side of the posterior aspect of the fetlock ; these 

 are rudimentary hoofs, each containing a small bone disconnected with the 

 skeleton. 



OMNIVORA. 



In the hog the concha is large, but variable in its arrangement, being 

 sometimes erect, sometimes flaccid. In connection with the eye the gland of 

 Harder exists. The skin is thick, often destitute of pigment, and has a very 



