384 THE ANATOMY OF VEETEBEATED ANIMALS. 



The blood corpuscles ai"e circular, and may have a 

 diameter of as little as -5-^nj of an inch. 



The foetal villi are gathered together into bunches or 

 cotyledons, which may present either a convex or a concave 

 face towards the uterus. They are received into persistent 

 elevations of the mucous membrane of the uterus, the sur- 

 faces of which present a reverse curvature. 



All the Cotylophora except Moschus, the true Musk Deer, 

 are provided with horns, but these horns are of two kinds. 

 The bony core, in the one case, is ensheathed in a strong 

 homy epidermic case ; while, in the other, the epidermis of 

 the integument which covers the core does not become so 

 modified. In the former kind of horn, the core becomes 

 excavated by the extension into it of the frontal sinuses, 

 whence the loiminants which possess such horns are not un- 

 f requently called Cavicornia (Antelopes, Sheep, Goats, Oxen). 

 As a general rule, the horny sheath persists throughout 

 life, growing with the growth of the core. But in the 

 remarkable Prong-horned Antelope of North America 

 {Antilocapra), the horny sheath is annually shed and re^jlaced 

 by a newly-formed one. 



Of the second kuid of horn, or that which acquires no 

 homy sheath, there are also two kinds. In the Giraffe, 

 the horn cores are attached over the coronal suture, at the 

 junction of the frontal and parietal bones, with which they 

 are not ankylosed; they persist throughout life, and are 

 always covered by a soft and hairy integument. 



In the Deer, on the other hand, the frontal bones grow 

 out into solid processes, which are, at first, covered by 

 soft and hpiry integument; generally they are developed 

 in the male sex only, but both sexes have them in the Rein- 

 deer. The horns attain their full size very rapidly, and 

 then a circular j'idge, which makes its appearance at a 

 short distance from the root of the horn and is called 

 the "burr," divides the horn into the "pedicel" on the 

 skull side of the burr, and the " beam" on the opposite side. 

 The circulation in the vessels of the beam now gradiially 

 languishes, its integument dies and peels off, and the dead 



