XIII 



PHYLUM CHORDATA 



459 



fibrous tissue ; the pecten is absent. In the internal ear the 

 principal point of difference is in the special development of the 

 cochlea. This part of the membranous labyrinth, instead of 

 retaining the simple curved form which it presents in the Bird, 

 is coiled on itself in a close spiral of two-and-a-half turns. The 

 spiral channel in the substance of the bone, in which this cochlear 

 spiral runs, contains three passages ; the middle one, much the 

 smallest, being the membranous cochlea, the uppermost the scala 

 vestibuli, and the lowermost the scala tympani. 



The special features of the middle ear with its auditory ossicles, and 

 of the external ear, have been already referred to (pp. 433 and 441). 



Urinogenital Organs. The kidneys are of somewhat com- 

 pressed oval shape, with a notch or hilus on the inner side. They 



ur 



ur 



FIG. 1108. Lepus cuniculus. The urinogenital organs ; A, of male ; B, of female ; from 

 the left side (half nat. size). The kidneys and proximal ends of the ureters, in A the testea, 

 and in B the ovaries, Fallopian tubes and uteri, are not shown, an. anus ; bl. urinary 

 bladder ; c. c. corpus cavernosum ; c. s. corpus spongiosum ; c. gl. Cowper's gland ; g. cl. 

 apex of clitoris ; g. p. apex of penis ; p. gl. perineal gland ; p. gl'. aperture of its duct on the 

 perineal space ; pr. anterior, pr'. posterior, and pr". lateral lobes of prostate ; ret. rectum ; 

 r. gl. rectal gland ; u. g. a. urinogenital aperture ; u. m. uterus masculinus ; ur. ureter ; 

 va. vagina ; vb. vestibule ; v. d. vas deferens. (From Parker's Zootomy.) 



are in close contact with the dorsal wall of the abdominal cavity, 

 the right being somewhat in advance of the left. Towards the 

 hilus the tubules of the kidney converge to open into a wide 

 chamber the pelvis which forms the dilated commencement of 

 the ureter. When the kidney is cut across, its substance is seen to 

 be divided into a central mass or medulla and a peripheral portion 

 or cortex. An adrenal (suprarenal) body lies in contact with the 



F F 2 



