208 



the gill function. In neither ease would there he any physiological reason 

 for the separation of the blood issuing from the conus. If the gills in the 

 fish do not entirely oxygenate the blood, and in some fish the fins apparently 

 assist in oxygenation, then the fish blood really corresponds to our notion 

 of "the mixed blood" (not fully oxygenated) in the higher forms. Here 

 again is a problem upon which no definite information may be given. 



In conclusion, my position on the quality of blood circulating in the 

 arteries of the vertebrates is that it is what may be termed "mixed" in 

 all forms from the embryo mammal and bird to the fish, and if there have 

 been advanced various theories on the mechanics of the passage of the 

 blood through the heart of a given form they have been based on the alleged 

 physiological necessity for a better quality of blood circulation in the head. 

 In other words the systemic arteries convey arterial blood only in the 

 mammal and bird after birth. I believe if one eliminates the idea that 

 the head must receive a better quality of blood (Sabatier scheme) the 

 whole doctrine of the character of the circulation in all forms of verte- 

 brates is not only simplified but placed upon a sound physiological and 

 developmental basis. 



LITERATURE. 



1. Brunei 1 , H. L. 



On the heart of lungless Salamanders, Jr. of Morph., Vol. XVI, No. 

 2, 1900. 



2. Gasch, F. R., Klassen und Ordnurgen des Thierreichs, Vol. 6, Sect. 4, 



p. 763. 



3. Lillie, F. R., Development of the Chick. Henry Holt, 1908. 



4. Parker and Haswell. Manual of Zoology, 1900, p. 422. 



5. Pohlman, A. G. 



The course of the Blood through the Heart of the Fetal Mammal. 

 Anat. Rec, Vol. Ill, No. 2, 1909. 



6. Wiedersheim, R. 



Comparative Anatomy of Vertebrates. Macmillan, 1907. 



7. Ziegenspeck, R. 



Die Lehre von der doppelten Einmiindung der unteren Hohlvene in 

 die Vorhofe des Herzens. Samml. Klin. Vortriige, Ser. XIV, Heft 

 II, No. 401. 



