No. 8.— The Blood Vessels of the Heart in Carcharias , Baja , and 
Amici. 1 
By G. H. Parker and Frederica K. Davis, 
Cambridge, Mass. 
With three plates. 
Introduction. 
In mammals the blood vessels of the heart are usually disposed 
in the following way: A right and a left coronary artery take 
their origins from the base of the aorta and are distributed, in the 
main, to the ventricular and auricular walls of their respective 
sides. The blood from these arteries is collected by a set of super¬ 
ficial veins arranged in three systems: a right, a left, and a median 
one. The right system is represented by the right or small coro¬ 
nary vein ; the median by the middle cardiac vein ; the left by the 
left or great coronary vein and the posterior cardiac veins. All 
these veins enter the coronary sinus, which in turn enters the right 
auricle. In addition to these superficial veins, the walls of the heart 
contain the numerous but small deep-seated vessels of Thebesius 
which, according to Langer (’81), open from the ventricles and 
auricles into a system of fine branches that connect with the coro¬ 
nary arteries and veins by means of capillaries. In the case of the 
veins, but not of the arteries, these connections may be by vessels 
larger than capillaries, as demonstrated by Pratt (’98, p. 92). 
The extent to which the blood vessels characteristic of the mam¬ 
malian heart occur in the lower vertebrates has never been fully 
ascertained. Presumably the most primitive conditions occur 
among fishes, and we have, therefore, undertaken the study of these 
vessels in three easily accessible species: Baja erinacea Mitchill, 
Carcharicis littoralis Mitchill, and Amici calc a Linn. The work on 
Raja and Amia was done in the Zoological laboratory of Rad- 
cliffe college at Cambridge; that on Carcharias was carried on at 
the laboratory of the United States fish commission at Woods Hole, 
Mass., and we take this opportunity of expressing our thanks to 
] Contributions from tlie Zoological laboratory of the Museum of comparative zoology 
at Harvard college. E. L. Mark, Director. No. 101. 
