THE ANATOMY OF BnW>S. — OOLOGY. 



217 



The Kidneys (Lat. rcnex, Engl, reins, adj. renal; figs. 10.3, 104, a; 10.5, x) differ iniicli 

 from tliiise (if niaminals in pliysioal characters, though identical in function, — that of strainiii;^- 

 (.iff from the lilood certain deleterious substances in the form of urea ; whence they are sometimes 

 called emulgeni organs. Their office of purification is analogous t(.i that of the limgs, wlijcli 

 dccarb(^inize the blood, and to some extent vicarious, as is that of excretory organs in general. 

 As the lungs are closely bound down to the thoracic region of the trunk, so are the kidney.s 

 impacted in tlie jielvic region, being moulded to the sacral inequalities of surface (p. 141). 

 They are paired, but sometimes connected across tlie median line by i-enal tissue ; they have no 

 special rinial artery, but derive their blood from various sources; and blood from them takes 

 part in the hepatic portal system, no reniportal being accomplished. They have little or notli- 

 ing of the particular mammalian configuration which has made " kidney-shaped" a comuKin 

 descriptive term ; being elongated, somewliat parallel-sided and rectangular, flattened bodies, 

 lobated into a few large compartments, and lobulated into many lesser divisions ; their figure 

 depends much upon that of the pelvis. They are very dark-colored, rather soft, easily lacenible, 

 and appear to the naked eye to be of a granular substance, without dis- 

 tinction of "cortical" and "medullary" portions. Nor is there any 

 " pelvis" of the kidneys in which the uriniferous tubules empty together 

 by numerous ducts as into a comuKjn ba,sin. Each vreter (figs. 10.3, h : 

 104, e; 105, y), or excretory duct, is formed by reiterated reunion of the 

 ii(huU uriniferi, after the manner of a pancreatic dnct ; each ureter passes 

 down behind the rectum and opens into the lower back part of the cloaca, 

 — much like a mammalian ureter into the base of the bladder. The 

 original cavity of the allautois remains to furnish no more of a urinary 

 Madder than some special dilatation of the cloaca represents; but this 

 rudimentary bladder, as distinguished from the ui-o-genital sinus in which 

 the ureters terminate alongside the sperm-ducts, is well marked in some 

 birds ; being in the ostrich, for example, a considerable enlargement of 

 the cloaca between the termination oi the rectum proper and the uro- 

 genital compartment of the sewer. The renal excretion is not watery 

 as in mammals, but semi-solid, and voided with the ftcces, of which it 

 forms part. 



The kidneys are capped by a pair of small yellowish bodies, the 

 mpra-renal caxmdes ox adrenals (figs. 103, /; 104, 105, fZ), the nature 

 of which is undetermined. They are chiefly interesting to the practical 

 ornithologist in their liability to be mistaken for testes in examining 

 specimens for sex (see p. 45), 



Fig. 105. — Uro-gc'ii- 

 ital organs of the domes- 

 tic cock; after Owen, 

 a, testis; ii, epididymis; 

 c, sperm-duct or vas de- 

 ferens; (7, adrenal; /.-. 

 cloaca; x, kidney; //. 

 ureter. 



Male Organs of Generation. — The testis {'Lut. testis, -pi. testes, 

 a witness; fig. 105, a) or testicle has been already sufficiently noticed as 

 to its general appearance and position (p. 46). As said above, it is the 

 essential male organ, consisting of the ])rimitive indifferent genital gland (fig. 103, e) in its 

 highest state of development as a tubular secretory organ, "connected with 'tlie remains of 

 the wolffian body as a part of its efferent structure (epididymis; fig. 105,?;) and with the 

 original wolffian duct as its vas deferens (figs. 103, d; 105, c), or efferent duct, by which the 

 semen is conveyed to the cloaca. The original glands normally remain paired, and both 

 are usually functionally developed to corresponding size, shape, and activity; they remain 

 in their embryonic situation in front of the upper part of the kidneys ; and such difference 



semen from e, the testis. In fig 104, i is the wolffian Iwdy, whose duct,/, disappears ; and g is tlie miillerian duct 

 becoming the oviduct, to convey the egg from c, the ovary. Thus e, flg. 103, and c, fig. 104, are the homologou.s 

 genital glands, becoming either testis or ovary : but the sperm-duct, d, flg. 10.3, is not the oviduct g flg 104 



