ORGANS OF DIGESTION. 125 



the walls of the abdominal cavity. It is a closed sac in the 

 male, but in the female the Fallopian tubes open into it. 



The ligaments are the layers of the peritoneum suspend- 

 ing other organs than parts of the alimentary canal. The 

 suspensory or falciform ligament extends from the caudal 

 surface of the diaphragm and the abdominal wall, to the sur- 

 face of the liver, which its line of attachment divides into 

 halves. The round ligament is the thickened free caudal 

 border of the suspensory ligament. It is the remains of a 

 vein which in fetal life joined the offspring to the mother. 

 A third ligament connects the dorsal border of the liver with 

 the diaphragm. The broad ligaments of the uterus are the 

 folds of peritoneum which embrace the uterus, the Fallo- 

 pian tubes, and the ovaries. The ovarian ligaments are 

 short cords extending from the ends of the uterine cornua 

 to the ovaries. The round ligaments of the uterus pass 

 from the sides of the uterus to the brim of the pelvis. 



The peritoneum is called a serous membrane because of 

 the colorless serum secreted by it. Other serous membranes 

 are the pericardium of the heart, the pleura lining the tho- 

 racic cavity and investing the lungs, and the synovial mem- 

 branes of the joints. Serous membranes invest only such 

 cavities as are not exposed to the air. All other cavities 

 are lined by mucous membrane. A serous membrane con- 

 sists of a layer of fibrous connective tissue covered by plate- 

 like endothelial cells. 



REMARKS ON THE MAMMALIAN DIGESTIVE SYSTEM. 



The digestive system of mammals varies somewhat 

 among the different groups. In carnivorous animals, as a 

 rule, the alimentary canal is much shorter than in herbivo- 

 rous. In the wildcat the canal is four times the length of 

 the body, while the canal of the sheep is twenty times as 



