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sent out through the right aorta, while the left aorta is purely arterial. 

 This is again the same scheme as we found in the mammal and results 

 in the head receiving a better quality of blood. 



Experiments were performed on three species of turtles to ascertain 

 if this condition prevailed. The plastron removed and the heart laid bare, 

 a double ligature was passed through the transverse pericardial sinus 

 and arranged to tie one at the distal, the other at the proximal edge of 

 the sinus. Next cornstarch granules suspended in normal salt solution 

 were introduced into the auricles during diastole; the auricle allowed to 

 contract, giving time to have the distal ligature ready to tie off; the distal 

 ligature was tightened during ventricular systole and immediately the 

 proximal one — isolating three columns of blood in the three vessels. These 

 were bled separately into watch glasses containing dilute acetic acid and 

 examined for the granules. It was found that granules injected into the 

 right and left, and in both auricles simultaneously, were always recovered 

 from all three efferent vessels. It must also be remembered that in the 

 turtle the fetal circulation is not unlike that found in the fetal bird — the 

 postcaval vein conveys the oxygenated blood, and if this segregation of 

 blood occurred as described in the adult, the head would receive only 

 venous blood. This objection also holds good in the Crocodilia, where, 

 according to Wiedersheim (6), the condition is as follows: "The blood from 

 the right ventricle passes into the pulmonary artei"y as well as into the 

 left aortic arch and, according as the septum ventriculorum is complete 

 or incomplete, is either entirely venous (Crocodilia) or mixed (other rep- 

 tiles). A complete septum ventriculorum thus appears for the first time 

 in crocodiles, in which, consequently, the right ventricle contains unmixed 

 venous blood and the left ventricle unmixed oxygenated blood, although, 

 as will be seen presently, an admixture takes place in the systemic ar- 

 teries." Again, according to this scheme, the head will receive a better 

 quality of blood because the carotids arise from the left aortic arch, but 

 again the objection as to the manner of transformation from the fetal 

 crocodile to the adult crocodile heart would arise. This form certainly 

 needs careful investigation. The purely venous blood would far exceed 

 the purely arterial, and the mixture at the foramen of Panizza might be 

 very complete. 



The amphibian circulation is naturally described on the basis of the 

 segregation of blood and must therefore fall into two classes, the anural 

 and the urodele. The description of the anural circulation is delightfully 



