258 Transactions. 



much thicker than usual ; in six they were about normal ; and 

 in four they were almost if not quite invisible.) 



4. The size, direction, and division of the external jugulars, 

 which may become very much looped along their courses. 



5. The division of the subclavian into its two branches. 

 (Out of fifteen frogs, seven had the division near or at the 

 shoulder, six about half-way between the shoulder and the vena 

 cava, and two near the vena cava.) 



6. The number of the renal veins. (These seem to vary 

 between five and seven.) 



7. The division of the anterior abdominal vein as it breaks 

 up into the lobes of the liver. (Out of fifteen frogs, five had a 

 large branch running into the left lobe, and the other ten had 

 no large branch, but each lobe was supplied by several smaller 

 branches.) 



8. The size of the lumbar veins. (Out of fifteen frogs, twelve 

 had them distinct, and in three they were very small.) 



9. The size of the ileo-lumbar veins. (In some specimens 

 they were large and distinct, while in others they were very 

 small and indistinct.) 



The lumbar and ileo-lumbar veins are often united by a 

 connecting vein. (Out of fifteen frogs, five had a distinct and 

 good connection, in seven a fair connection, and in three there 

 was no connection at all visible.) 



Veins from the Skin. 



If fig. 1 be compared with Ecker's* it will be seen that the 

 veins coming from the skin differ widely in the two frogs. Ac- 

 cording to Ecker, with the exception of three pairs of parietal 

 veins near the posterior end of the abdomen, all the blood from 

 the skin is returned through the large cutaneous veins. 



Now, in Hyla aurea there are four centres from which the 

 blood from the skin is returned, and this is done by four dis- 

 tinct pairs of veins — namely, the external jugulars, the cutaneous, 

 the parietals, and the pelvico-cutaneous — the first three being 

 especially noticeable. 



1. The external jugular veins (e.j.) are a pair of very large 

 and often much-twisted vessels running across the body from 

 the angles of the jaws towards the median line just above the 

 pectoral girdle and then disappearing through the body-wall. 

 Some of their branches — namely, the mandibular and several 

 other large veins — bring in the blood from the skin around the 

 head and shoulders. 



* Ecker's " Anatomy of the Frog," Eng. trans., p. 244, fig. 161. 



