106- 



fluence form the commencement of the ureter, which descends 

 along the surface of the kidney, and posterior wall of the rectum, 

 and terminates in that part of the cloaca called the urethro-sexual 

 cavity. The space between their termination and that of the rec- 

 tum is large in the owl and many aquatic birds, and is looked upon 

 by some as a rudiment of urinary bladder. 



The supra-renal capsules are small, of a bright yellow colour, 

 and placed on the inner and upper part of each kidney, in contact 

 with the testicle or the ovary. They are erroneously supposed by 

 some to have some functional relation to the generative system. 



MAMMALIA. 



The kidneys are lobulated in the cetacea, seals, otters, bears, the 

 elephant, the ox, &c, as in the human foetus. In the otter each 

 kidney consists of about ten lobules; in the bear of about fifty, and 

 in the seal as many as a hundred and thirty. They present a lobu- 

 lated appearance in many other mammalia during the early periods 

 of existence. The ureters enter the bladder in an oblique direction, 

 a little behind its neck, in all the animals of this class, with the ex- 

 ception of the echidna and ornithorhynchus, in which they open 

 into the urethra near its commencement, so that the urine must ?G- 

 ascend to the bladder, as in the chelonian reptiles. In the mamma- 

 lia generally the bladder lies more loose in the abdomen than in 

 the human subject, owing to its more perfect peritoneal investment. 

 For the greater part it is more muscular and less capacious in the 

 carnivora than in the herbivorous tribes. In the rodentia, however, 

 it is small and fleshy. The shape of the bladder will be found to 

 vary in obedience to age, sex, and species, the younger the animal, 

 however, the more elongated will it be found, and in the human 

 embryo it is cylindrical, tapering towards the urachus above, and 

 the urethra below. 



The renal capsules, like the kidneys, are lobulated in the cetacea, 

 and other aquatic mammalia, and are found relatively very large 

 in the young of animals possessing them. The urethra, as in the 

 human subject, consists of a membranous or muscular, and of a 

 spongy portion, the former receiving the accessory secretions. In 

 the boar and many ruminants these two portions join at an angle. 

 The corpus spongiosum arises by two roots in most of the marsu- 

 piata, and in the kangaroo, the urethra runs through the centre of 

 the penis to its extremity. 



RECAPITULATION. 



1. In the great invertebrate division of animals, the functions of 

 the kidneys seem to be performed by other parts, as the surface of 

 the body generally, and certain glands. 



2. Kidneys exist in all fishes, but a urinary bladder is confined 

 to the cartilaginous tribes. 



