IS MAMMIPEROUS ANIMATES, 



perpendicular line, and in Oxen, Horses, and a ^t\f 

 others, it forms a transv^-rse bar. The opening con- 

 tracts during the day, that the very sensible retina 

 may not be irritated by the rays of light ; and is ex-. 

 panded in the dark to allow as many rays as possiblg 

 to pass. 



The ears are openings generally accompanied by 

 a, cartilage which defends and covers them, called the 

 external ears. In aquatic animals the latter are want- 

 ing, the sounds in them b ing transmitted merely 

 through holes, which have the name of auditory holes, 

 Tlie most defenceless animals are very delicate in 

 their sense of hearing, as are likewise most of the 

 beasts of prey. In wild animals the ears are erect and 

 somewhat funnel shaped, capable of having their 

 opening turned towards the quarter from whence the 

 sounds proceed, but in those that are tame or domes- 

 tic the ears are, for the most part, long and pen- 

 dulous. 



The head is joined to the body by the neck ; and 

 all those animals that often extend their arms or an- 

 terior feet forward, either to seize things, as the 

 Monkies, or to fly, as the Bats, have, annexed to the 

 upper part of the thorax, clavicles or collar bones. 

 The clavicle of the Mole is particularly remarkable 

 on account of its thickness, which exceeds its length. 

 The collar-bones are wanting in those animals that 

 use their anterior extremities for progressive motion 

 only ; and there are rudiments of them in such as 

 hold a middle station betwixt these two different 

 orders. 



Most of the Mamraiferous Animals walk on four 



