Chap. III.] GENERAL ANATOMY. 29 



median aperture leading into the large bi-lobed urinary bladder 

 (7, Ur. BL). Into it the urinary fluid, therefore, does not pass 

 directly from the ureters, but indirectly through the cloaca. 



The genital organs of the male are the testes (1 and 8, Ts.). 

 They are closely connected with the kidneys by a mesenteric 

 membrane (the mesorchium), in which fine white lines may be 

 seen, which are the ducts by which the seminal fluid is conveyed 

 to the kidney, to pass thence by the ureter, which should there- 

 fore be termed the urino-genital duct in the male. 



The genital organs of the female are, (1) the large ovaries 

 crowded in the breeding season with large ova, and suspended 

 by the mesoarium, and (2) the coiled oviducts. The oviducts are 

 anteriorly thick and glandular and swell up in water ; posteriorly 

 they are thin-walled, and open into the cloaca by slits in its 

 dorsal wall, just in front of the apertures of the ureters. The 

 oviducts do not open into the ovaries, but open at the very 

 anterior end of the pleuro-peritoneal cavity close to the base of 

 the lungs. The ripe ova are shed into the pleuro-peritoneal 

 cavity, and escape thence by the oviducts. 



The yellow finger-like processes seen in both sexes are the 

 fat bodies (corpora adiposa). 



5. The Nervous System. In the subvertebral lymph space 

 there are parts of two nerve systems. 



On either side of the dorsal aorta is a delicate dark thread, 

 from which minute threadlets pass off to much more conspicuous 

 white threads passing backwards beneath and on either side of 

 the urostyle. The delicate dark thread belongs to the sympathetic 

 nerve system (8, Sy.). The larger longitudinal white threads 

 belong to the cerebro-spinal nerve system. They form part of the 

 lumbo-sacral plexus (8, I. s. p.\ from which the nerves of the hind- 

 leg take their origin. Further forward, two of the spinal nerves 

 form a brachial plexus running out to the arm. Other spinal 

 nerves will be seen between these two plexuses. All these 

 spinal nerves take their origin in the myelon or spinal cord, which 

 lies in a dorsal cavity within the arches of the vertebrae of the 

 backbone. In the neighbourhood of the head there are cranial 

 nerves, taking their origin in the brain, which lies within the 

 skull. 



