OF THE KIDNEYS. 161 



large trunk, where the motion of the blood is very rapid, and where 

 they are obliged to terminate soon in the ultimate branches, which 

 continue the rapidity of the blood's motion in them, — there we find that 

 the arteries necessary for the performance of the secretion of urine, take 

 on a little twist, convolution, or spiral turn, called ' crypta,' intended 

 for the retardment of the blood's motion, to allow of secretion ; but the 

 termination of every artery in the kidney has not these cryptae ; and as 

 they are confined to the external parts of the kidney, they give a peculiar 

 appearance to this part distinguishable from the rest, whence the sub- 

 stance of the kidney in this order of animals is divided into the two 

 kinds above mentioned, viz. the cortical and the tubular. 



The veins of the kidney in common follow the arteries : however, 

 there are exceptions to this rule. In the lion kind, cat kind 1 , as also 

 in the hyaena 2 , we find that perhaps one half of the veins get on the 

 external surface, and are either strongly attached to, or pass in a 

 doubling of the capsule of the kidney, and then pass along like the veins 

 of the pia mater, afterwards joining the trunks from the inside just as 

 they pass out. 



The excretory ducts of kidneys in general may be reckoned inter- 

 mixed everywhere with the secretory, forming a regular ramification of 

 branches and trunks. The ultimate branches are of two kinds ; first, 

 where the excretory, or what may be called the first order of ducts, 

 arise in every part of the kidney, then unite and form trunks, which 

 may be called the second order, and these unite and form the third, and 

 so on, forming at last the ultimate trunk, called the ureter, as in Fish 3 , 

 Amphibia 4 , and Fowl 5 . The second is where the secretory and excretory 

 are pretty distinct, not intermixed as in the first, the secretory being 

 the most external, the excretory the most internal 6 ; and where the 

 excretory do not at all unite into larger and larger branches, forming in 

 the end one common trunk, as in the first ; but where they all open into 

 a cavity or reservoir, called pelvis, which is placed in a pretty deep 

 sidcus in the inner edge of the kidney 7 . 



The mode of opening into this reservoir admits of some variety, but 

 may be divided first into two species. The first species is where the 

 excretory duets, after forming the second and third order, open into the 

 pelvis on a concave surface, as in the horse, ass, &c. 8 ; the second is 

 where they form a projection or projections, called mamma or mammilla, 

 which are projected into this cavity, and the excretory ducts open on 



1 [Hunt. Preps. Nos. 1200-1205.] 2 [lb. No. 1206.] 



3 [lb. No. 1186.] 4 [lb. No. 1192.] 



5 [lb. No. 1196.] 6 [lb. No. 1222.] 



7 [lb. No. 1218.] s [lb. Nos. 1208-1216.] 



