OF THE KIDNEYS. 159 



obnoxious, becoming the common-sewer of the constitution ; but those 

 parts must be carried off by a change being performed in them, consti- 

 tuting a secretion. 



These bodies probably do not exist in every animal ; at least they are 

 not to be found in every one, most of the inferior orders of animals 

 having visibly no such bodies, which is one mark of their inferiority ; 

 although it is probable that in them other common parts may serve the 

 same purpose, or perform the same action ; for instance, it is probable 

 that the intestines of such perform the same office. 



As these bodies, in those animals which possess them, are to perform 

 an office peculiar to themselves, they are distinct parts from all others 

 in the body. 



They are, from Fish upwards, in pairs ; but below Fish, as in the 

 cuttle-fish, snail, &c, there appears to be only one. Their situation in 

 the body varies in different animals. From Fish upwards they may be 

 said to be placed within the belly of the animal, near to the back ; but 

 below them, in the inferior orders, where both their number and situa- 

 tion are not the same with those where they are evident, it becomes 

 uncertain whether such bodies, whose use is not immediately seen or 

 obvious, are the kidneys or not ; nor is it so determined where they 

 may be placed; as, for example, in the cuttle-fish the kidney is in 

 the anterior part of the belly, in the snail by the lungs 1 . 



In some orders of animals they are very circumscribed bodies, being 

 enclosed in a proper membrane or capsule, as in the most perfect orders, 

 and in some degree so in Amphibia ; but in Fowl they are more obscure, 

 being placed in the hollows of the pelvis ; while in Fish they are still 

 less detached, lying all along the sulcus made by the spine, and are 

 closely attached to the parts behind, not having there any particular 

 capsule. 



In some animals the kidney is a very oblong body, extending in 

 length for a considerable way, and very narrow, as in some Fish 2 , while 

 in other animals it is almost globular, as in the leopard 3 . 



In some the external surface is smooth and regular, as in the human 

 subject ; in others covered with large branches of veins ramifying on it, 

 as in the lion tribe, &c. In others, again, the whole mass is lobulated 

 into several parts, and very irregular on its surface. 



The consistence of the kidney is in general a pretty solid substance, 

 but most so in the most perfect animal, appearing to become less and 

 less so to the inferior orders, for in fish they are of a very tender sub- 

 stance, and still more so in the snail. 



1 [Hunt. Prep. No. 1176.] 2 [lb. No. 1185.] 3 [lb. No. 1202.] 



