THE FROG 9 1 



it to swell to an inconvenient size, the use of formalin for 

 hardening and preserving this preparation is not advisable; 

 the dissection should be placed directly in alcohol. A similar 

 preparation should be made of the female reproductive sys- 

 tem showing the eggs in the uteri ; females in the right con- 

 dition for this preparation may be found in the early spring. 

 Of greater importance than the above is the making of 

 permanent preparations showing the urogenital system re- 

 moved from the body so that all its parts may be separated 

 out clearly and in particular the ducts shown in their rela- 

 tion to the cloaca. The figures in Leuckart's charts on the 

 anatomy of the frog (Kny Scheerer and Co.) will best serve 

 as a guide in making these preparations. Using fresh ma- 

 terial, remove the urogenital system entire, together with 

 the large intestine and especially the cloaca, as follows : Dis- 

 sect the bladder free from the posterior body wall, cut the 

 cloaca across as far back toward the anus as possible, dis- 

 sect the entire large intestine free from the dorsal body wall, 

 and cut it across where it is joined by the small intestine. 

 Remove the large intestine, together with the cloaca, blad- 

 der, kidneys, gonads, fat bodies and the ducts which enter 

 the cloaca. Spread out the preparation on a wax plate to be 

 used in mounting it (see directions for the digestive sys- 

 tem), and clean up the peritoneum and blood vessels about 

 the ureters. Trace the ducts to their union with the cloaca, 

 slit the cloaca open along a ventro-lateral side and find the 

 openings of the ducts and the bladder; insert bristles into 

 the openings, using differently-colored bristles to distinguish 

 the various kinds of openings. Insert bristles into the open- 

 ings of the oviducts at their anterior ends. After arranging 

 the various parts in suitable positions so that they may be 



