118 COMPARATIVE ANATOMY. 



and disappears after expulsion of egg. The oviduct, when 

 quiescent, is straight, but when the female is under sexual 

 excitement, convoluted. After receiving various glandular 

 appendages designed to secrete accessories to the eggs, it 

 empties into the cloaca. Clitoris well developed in Struthio 

 (ostrich). The testicles, two in number, are placed at upper 

 extremity of kidney. They vary in color, a shade of yellow 

 being the prevailing hue. Yas deferens generally slightly 

 convoluted, and empties into cloaca. Penis is an extra- 

 version of mucous membrane having erectile tissue in its 

 walls, as in Gallus (cock), or very long, convoluted, and 

 grooved along dorsal surface, as in the Natatores. 



Mammalia. The ovaries are always two in number. Orni- 

 ihorhynchus (duck-bill), right small and imperfect. Bodies 

 oval, compressed; stroma rather dense, fibroid. In Impla- 

 centalia, the oviduct (Fallopian tube) expands at lower por- 

 tion (uterus) in Monotremata, and afterwards abruptly con- 

 tracts to open, in common with the urethra, with the fellow 

 of opposite side in a wide passage (urogenital canal), which 

 leads to a second chamber yet in advance, the vestibule. 

 The rectum joins the vestibule at its inferior portion to form 

 the cloaca. In Marsupialia the oviducts, as they descend, 

 enlarge to open by contracted papillated extremities into the 

 vagina, which is peculiar in having a central pendulous 

 chamber resembling a uterus (vaginal cul-de-sac), which may 

 be large, as in Macropus (kangaroo), or small, as in Didelphis 

 (opossum). From either side of this, at its upper part, two 

 vaginal canals are given off, which, converging, empty into 

 the urogenital canal below. 



In Placentalia the two oviducts open into a median mus- 

 cular cavity, the uterus. This is markedly prolonged at its 

 angles (cornua) in majority of mammals slightly cornuated 

 in Quadrumana (monkeys), not at all in human female. 

 Uterus opens into a second canal (vagina) which terminates 

 externally, receiving near its verge the urethra. Clitoris, 

 large in Quadrumana, and sometimes possesses a bone. 

 Longitudinal septum occasionally present in vagina. A 

 powerful sphincter vaginae present in the bitch. 



