40 LABORATORY MANUAL FOR ELEMENTARY ZOOLOGY 



ligament. It sends down two tail-like processes to the duodenum, and another 

 process, the hepatic process, along the dorsal surface of the posterior part 

 of the left lobe of the liver, where it extends almost to the gall bladder 

 (Holmes, p. 151). 



6. The bile duct. The common bile duct runs through the pancreas and 

 enters the duodenum by way of the second of the tail-like processes mentioned 

 above, i.e., the one farthest away from the pylorus. Dissect away the pancreas 

 in this region, and find the slender white duct, about the size of a sewing thread. 

 Trace the duct up through the pancreas into the hepatic process of the pancreas. 

 Here it receives a number of small hepatic ducts from the posterior part of the 

 left lobe. To find these dissect away the substance of the liver. Follow the 

 bile duct to the gall bladder, where it again receives hepatic ducts from the right 

 lobe and the posterior part of the left lobe. Two ducts, the cystic ducts, emerge 

 from the gall bladder. One of them unites with the hepatic ducts near by, and 

 the other is continuous with the common bile duct. Consult Holmes, Fig. 42, 

 p. 152, and work out the hepatic and cystic ducts as well as you can. It is not 

 practical to find the pancreatic ducts. 



7. The large intestine. The ileum enlarges abruptly into the large intestine, 

 which runs straight to the anus. The upper part of the large intestine is called 

 rectum; the lower part, cloaca. Cut through the pelvic girdle so as to expose 

 the intestine all the way to tHe anus. Find the origin of the urinary bladder 

 from the ventral wall of the cloaca. The cloaca also receives the ureters and 

 oviducts. 



Draw the entire digestive tract, showing all its parts, with the lobes of the 

 liver turned forward. Draw in the common bile duct in proper position in the 

 pancreas, and the hepatic and cystic ducts as far as you have been able to find 

 them. 



B. THE URINOGENITAL SYSTEM 



Remove the digestive system, leaving the large intestine in place (Holmes, 

 chap, xi, pp. 212-18). 



i. Male urinogenital system. Strip off the peritoneum wherever necessary 

 to expose the urinogenital system. Each testis is an oval body attached by a 

 fold of peritoneum, the mesorchium, to the adjacent kidney. From each testis 

 spring several delicate ducts, the vasa eferentia, which run in the mesorchium 

 and penetrate the kidney. The vasa efferentia are really outgrowths of the 

 Malpighian bodies of the kidney, which extend out and connect with the testes. 

 By holding up the mesorchium to the light, the vasa efferentia may usually be 

 seen. The vasa efferentia after entering the kidney eventually connect with the 

 ureter by a route which differs in different species of frogs. From the posterior, 

 lateral edge of each kidney extends the ureter. Find it and trace it to the cloaca. 

 Alongside and parallel to the lateral edge of the kidney runs a vestigial oviduct, 



