174 ELEMENTARY BIOLOGY. [CHAP. 



The liver is very large, and is divided into two lobes 

 united by a mere bridge, dorsally and anteriorly. The left 

 lobe is further subdivided into two. The gall bladder is 

 attached to the posterior and dorsal face of the right lobe. 

 The biliary duct opens into the duodenum, at some distance 

 behind the pylorus, and its termination is embraced by the 

 base of the slender pancreas. 



The rounded spleen lies in the mesentery, projecting 

 more to the left than to the right side, just above the point 

 at which the duodenum passes into the ileum. 



The apparatus of circulation in the Frog consists of the 

 blood and lymph vessels and their contents. 



The lymph is a colourless fluid containing colourless 

 nucleated corpuscles which exhibit amoeboid movements : 

 it is contained partly in large spaces immediately beneath 

 the integument; in the pleuroperitoneal cavity and pro- 

 bably in the other serous cavities; and, partly, in capillaries 

 and larger trunks which are interlaced with and accompany 

 the blood-vessels. The largest of the trunks is the great 

 sub-vertebral lymph-sinus, which lies between the layers of 

 the root of the mesentery and communicates by small pores 

 with the pleuroperitoneal cavity. There are four lymph- 

 hearts. 



The blood consists of a colourless plasma which contains 

 colourless corpuscles, similar to those of the lymph, and in 

 addition a great number of oval nucleated red corpuscles. 

 It is contained in the blood-vessels, which consist of capil- 

 laries, arteries and veins, the two latter being connected on 

 the one side by the capillaries and, on the other, by the 

 heart into which they open. The lymphatics and the 

 blood vessels are brought into connexion with one another 

 by communications between the anterior lymph-hearts and 



