as follows: The net of the previously developing blood 

 vessels is converted into a system of vascular stems and 

 branches, "highly refined decoration of the vascular mem- 

 branes"; the stems reach the fetus, and the smallest 

 branches reach the peripheral circulation. The arterial 

 stems go out from the fetus in a straight angle, soon 

 divide into three or four branches, while an endless number 

 of small branches fall into the terminal series and also 

 form numerous anastomoses with the thin venous branches. 

 The terminal or peripheral blood circulation, which is 

 called terminal venous circulation, is devoid of vessel 

 walls. From the terminal venous circulation, two or three 

 veins originate, directed to the fetus along its longitudinal 

 axis. The upper descending vein, which is usually duplicated, 

 is a continuation of the terminal sinus; it descends to the 

 head of the fetus, lies on the head portion, and moves close 

 to the heart. The lower ascending vein begins with numerous 

 small branches from the opposite end of the terminal sinus, 

 ascends beside the tail of the embryo, and joins the descend- 

 ing veins near the heart. 



The heart, which is located on the left side of the 

 fetus and covered with the head portion, is composed of three 

 connected cavities. The first of these cavities is the 

 auricle, the second is the ventricle, and the third is the 

 aortic bulb. The ball-shaped auricle is connected with veins 

 backwards, and anteriorly connected with the continuation of 

 the ventricle. The latter is connected by means of a narrow 

 duct to the widest aortic bulb, from which a narrow cylindrical 

 canal passes into two or three aortic stems. The aorta goes 

 along in a large arch to the heart hole, forming a single trunk 

 which then divides into two, each of which covers a vertebra. 

 By getting narrower, it is lost in the tail region. From 

 these arterial trunks, somewhat further to the middle of the 

 fetus, originate two arteries of the vascular area.^ 8 Blood 

 flow in the vessels begins from the ventricle, where the 

 blood passes along the aorta into two lateral arteries. 

 From their smallest branches it goes partially into the 

 terminal sinus and partially into minute branched veins, and 



28. This place in the dissertation is accompanied by an 

 extensive footnote, in which Pander talks about the 

 erroneous description of the embryonic vessels in 

 the works of Tiedemann, Wolff, and especially Oken. 



256 



