XIII 



PHYLUM CHORDATA 



541 



A coecum situated at the junction of the large and small intes- 

 tines is usually present, but varies greatly in extent in the different 



orders and families. 



It is much larger in 



vegetable feeding 



than in carnivor- 

 ous forms, and 



among the former 



it is those that 



have a simple 



stomach, such as 



the Rabbit, that 



have the largest 



caecum. Hyrax dif- 



ers from all the 



rest of the class in 



having a pair of 



supplementary 



coeca situated some 



distance down the 



large intestine. A 



coecum is absent in 



the Sloths, some 



Cetacea, and a few 



Carnivora. 



The Prototheria resemble Reptiles, Birds, and Amphibia, and 



differ from other Mammals in the presence of a cloaca, into which 



not only the rectum, but the urinary and genital ducts open. In 



the Marsupials a com- 

 mon sphincter muscle 

 surrounds both anal 

 and urino-genital aper- 

 tures ; in nearly all the 

 Eutheria the apertures 

 are distinct, and separ- 

 ated from one another 

 by a considerable space 

 the perinceum. 



The liver (Fig. 1132) 

 consists of two parts or 

 main divisions, right 

 and left, incompletely 



FIG. 1132. Diagrammatic plan of the liver of a Mammal Separated from One 



(posterior surface), c. caudate lobe ; cf. cystic fissure ; dv. rj nn t>,p r V, v fl fi5?lirf 



ductus venosus;V gall-bladder; Ic. left central lobe; anotne DV a ] 



II. left lateral lobe ; llf. left lateral fissure ; p. portal vein termed Um0^l^Cal OWing 

 entering transverse fissure; re. right central lobe ;rl. right , . . 



lateral lobe ; rlf. right lateral fissure ; s. Spigelian lobe ; to itS marking tfie 



Lyd U ekkerO al ^ *' *' ^^^ position of the fetal 



Fio. 1131. Diagrammatic section of the stomach of the Porpoise. 

 , oesophagus ; b, left or cardiac compartment ; c, middle com- 

 partment ; d and , the two divisions of the right, or pyloric 

 compartment ; /, pylorus ; g, duodenum, dilated at its com- 

 mencement ; li. bile-duct. (After Flower and Lydekker). 



