158 PERISSODACTYLA. 



the caecum for a little way, and then begins to make its spiral turns, 

 which, are as represented in the figure 1 . 



The spiral turns of the colon are not seen in the natural state of the 

 mesentery, only the caecum with the fold of the colon which is upon 

 the caecum, and the last turn of the colon where it ascends to cross the 

 mesentery. To see the spiral turns, the mesentery must be turned to 

 the right. That part of the colon which runs along the mesentery 

 passes pretty near the root of that membrane, by which means it is 

 much shorter than in many others of this class. There are two azygos 

 veins. 



The udder is made up of two distinct parts, viz. a right and a left ; 

 each part having two nipples : they are as distinct and independent of 

 one another as the breasts in a woman. 



The penis of a slink bull-calf has not the turn towards the posterior 

 end, as in the old bull : hence it would appear that that turn is made 

 by the retractor muscles of the penis, -when the penis becomes too long 

 for the distance between the anus and prepuce, even in a relaxed state. 



Horns and Claws. — The horns and claws of animals are formed in 

 strata not parallel to their axis, but oblique, tending towards a point in 

 the axis, and which point is towards the point of the horn, &c, as 

 when the horn becomes long, the first always scales off, by which 

 means the point is always kept sharp. 



[Order Perissodactyla. 

 Suborder Solidungula. 



Family EQU1DJE.] 



The horse [tribe] has the fewest in number of species of any : I do 

 not know if we have any more than the horse and ass : whether there 

 are two species of ass I do not "know 2 . . 



Of the Horse [Equus Caballus, Linn.]. 

 The tendons below the os calcis in the hind-foot, and the tendons 



1 [Home, Comp. Anat. i. p. 463, tab. cxviii. Hunter preserved preparations of 

 most of the organs of th'e common ox. See Physiol. Catal. 4to. vol. v. p. 258.] 



- [It does not appear whether Himter was acquainted, at this time, with the zebras 

 and quaggas ; or in what light he viewed them. Modern zoologists refer the wild 

 asses of Asia to more than one species.] 



