34 Cincinnati Society of Natural History. 
the roof of the outer chamber of the right pericardial cavity 
just below the right vagus nerve, and enters the roof of the 
portal heart near the posterior end. (See Fig. XVI, supr int.) 
The slit through which the blood enters is diagonally placed, 
and guarded by a pair of semi-lunar valves, like those of the 
anterior portal. 
The portal heart (Figs. X, XVI, XVII. XVIII, XIX, H.) lies 
in the pericardial fold which forms the septum in the right 
pericardial cavity. It is an elongated sac (1-2 cm. in length), 
somewhat irregular in shape and variable in size. It stretches 
diagonally across the pericardial cavity, and lies nearly oppo- 
site the ventricle (cf. Fig. X). Amteriorly it receives the 
anterior portal vein; toward the posterior end it receives 
the supra-intestinal vein. Both these enter dorsally. At its 
posterior extremity the portal heart empties into its efferent 
vessel, the common portal vein. ‘The opening into the common 
portal vein is guarded by a pair of strong semi-lunar valves 
(Fig. XVI, cp), which are placed laterally, and like the other 
valves previously described, prevent any reflux of blood 
during the circulation. 
Johannes Miiller was mistaken in his statement that no 
muscle fibers exist in the portal heart of Bdellostoma.* The 
wallis quite muscular, fully as much as that of the auricle. As 
in the latter, the inner surface of the wall of the portal heart 
is made irregular by muscular and fibrous trabecule, which 
project from the surface. The muscle fibers are ad?stinctly 
striated, and their nuclei seem to lie on the sides of (not 
within) the contractile fibers. 
The common portal vein (Figs. XVII, XVIII, XIX, ep) con- 
tinues backward and inward toward the median line. It 
passes above the anterior lobe of the liver, to which it gives 
off ventrally a large branch which descends almost vertically 
alongside the hepatic duct of the anterior lobe. (XI, cpa). 
The main trunk of the common portal vein then crosses the 
median line to the left side and passes backward and down- 
ward alongside the hepatic duct of the posterior lobe. (Fig. 
XI, cpp.) About the center of the dorsal surface it enters 
*Vergl. Anat. der Myxinoiden (1834). Later Miiller observed the pulsations of the 
portal heart in living Myxine. Untersuchungen tiber die Kingeweide der Fische 
(1842). 
22 
