LYMPH-HEARTS 129 



times of pumping of each ventricle, position of open- 

 ings, and position of membranes or valves in the 

 region — the crocodile, when breathing the air, is 

 really warm-blooded in the front part of the body 

 and cold-blooded everywhere else, but, by means of 

 this leak, he is wholly cold-blooded when he is under 

 the water holding his breath. At least some students 

 have so thought, and the purpose of this hole implies 

 something like it. If true, it is one of the most won- 

 derful cases of adaptation to variable conditions found 

 in Nature. 



To be wholly hot-blooded the crocodilians would 

 have to do away with the artery running to the body 

 from the right ventricle, and then, of course, close the 

 hole in that runnino^ from the left. Then the condi- 

 tion would be similar to those in the birds and mam- 

 mals, and the four-chambered heart would mean more 

 than a mere prophecy. Had both arteries run from 

 the left ventricle, however, and the hole between 

 them remained, the animal would still have been 

 hot-blooded, if such lungs could have made it so. 



The author trusts he may be pardoned for really 

 trying to show the different causes which may bring 

 about hot and cold blood, since most popular works 

 say little about it. 



Lymph-Hearts 



In reptiles there are lymph-hearts at the root of 

 the tail as in amphibians and some birds ; and in 

 all these low creatures and some mammals, there are 

 places — usually in the armpit — where the blood-veins 



