COMPARATIVE ANATOMY. 



In mammalia which have horns, these 

 parts grow oh particular processes of cer- 

 tain bones of the cranium. In the one- 

 horned rhinoceros, they adhere to a rough 

 and slightly elevated surface of the vast 

 nasal bone. The front horn of the two- 

 horned species has a similar attachment ; 

 the posterior rests on the os frontis, as 

 those of the horned pecora do. Two 

 kinds of struqture are observed in the 

 latter ; there are either proper horns, as 

 in the genera of the ox, goat, and ante- 

 lope ; or bony productions, as in the ge- 

 nus cervus, which includes animals of the 

 deer kind : these are also called horns in 

 English, or sometimes antlers; in French, 

 bois de cerf. In the former, the external 

 table of the frontal bones is elongated 

 into a process, which contains a continu- 

 ation of the frontal sinuses, except in 

 the antelope. Its external vascular sur- 

 face secretes the horn, which covers this 

 process like a sheath. In the stag kind 

 (in the male only in' most genera) the 

 frontal bone forms a short flattened pro- 

 minence, from which the proper antler 

 immediately shoots forth. It is renewed 

 every year, and is covered, during the 

 time of its growth, with a hairy and very 

 vascular skin. 



Castration, or any essential injury of the 

 organs of generation,impedes the growth, 

 alters the form, or interrupts the renewal 

 of the horns. 



The word horn, which is frequently ap- 

 plied in English to the antlers of the deer 

 kind, as well as to the real horns of other 

 genera, would lead to a very erroneous 

 notion on this subject. The antler is a 

 real bone ; it is formed in the same man- 

 ner, and consists of the same elements 

 as other bones ; its structure is also the 

 same. 



It adheres to the frontal bone by its ba- 

 sis ; and the substance of the two parts be- 

 ing consolidated together, no distinction 

 can be traced, when the antler is com- 

 pletely organized. But the skin of the 

 forehead terminates at its basis, which is 

 marked by an irregular projecting bony 

 circle ; and there is neither skin nor peri- 

 osteum on the rest of it. The time of its 

 remaining on the head is one year: as the 

 period of its full approaches, a reddish 

 mark of separation is observed between 

 the process of the frontal bone and the 

 antler. This becomes more and more 

 distinctly marked, until the connection is 

 entirely destroyed. 



The skin of the forehead extends over 

 the process of the frontal bone when the 

 antler has fallen : at the period of its rege- 



neration, a tubercle arises from this pro- 

 cess, and takes the form of the future ant- 

 ler, being still covered by a prolongation 

 of the skin. The ^ructure of the part 

 at this time is soft and cartilaginous; it 

 is immediately invested by a true perios- 

 teum, containing large and nunr roas ves- 

 sels, which penetrate the curtilage in 

 every direction, and by the gradual depo- 

 sition of ossific matter convert it into a 

 perfect bone. 



The vessels pass through openings in 

 the projecting bony circle at the base of 

 the antler : the formation of this part, pro- 

 ceeding in the same ratio with that of me 

 rest, these openings are contracted, and 

 the vessels are thereby pressed until a 

 complete obstruction ensues. The skin 

 and periosteum then perish, become dry, 

 and fall off; the surface of the antler re- 

 maining uncovered. At the stated period 

 it falls oft', to be again produced, always 

 increasing in size. 



The skeleton of quad'-upeds deviates 

 more from that of man. in the form of the 

 lower jaw bone, than in any other purt. 

 This diffierc nee consists chiefly in the want 

 of a prominent chin ; that peculiar cii.*r c- 

 teristic of the human countenance, which 

 exists in every race of mankind; and is 

 found in no other instance whatever. Man 

 has also the shortest lower jaw in compa- 

 rison with the cranium ; the eK phant, per- 

 haps, approaching the nearest to him in 

 this character. The same bone is further 

 distinguished by the peculiar form and 

 direction of its condyle. The articulation 

 of these processes vnries according to the 

 structure of the masticating organs. They 

 are both situated in the same straight 

 horizontal line in the ferae ; their form is 

 cylindrical ; and they are completely 

 locked in an elongated glenoid cavity, 

 whose margins are so extended before 

 and behind the condyle, that all rotatory 

 motions are rendered impossible, and 

 hinge like movements only allowed. This 

 structure is most strikingly exemplified 

 in the badger, where the cylindrical con- 

 dyles are so closely embraced by the mar- 

 gins of the articular cavity, that the lower 

 jaw (at least in the adult animal) is still 

 retained in its situation, after the soft 

 parts have been entirely removed by 

 maceration. In many herbivorous ani- 

 mals (in the most extensive sfnse of the 

 term) these condyles are really rounded 

 eminences ; viz. in the elephant and bea- 

 ver. Their surface is flattened in the 

 pecora, which have also the lower jaw 

 narrower than the upper, so that the two 

 sets of teeth do not meet together when 



