CARDIAC LOOP IN RABBIT 



31 



are still separate mark out the line of fusion of the two primitive 

 tubes, and it is thus quite evident what portions of the cavity- 

 are derived from the right cardiac vessel and what portions from 

 the left. 1 



The elements represented are: a) the sinus venosus at the 

 confluence of the vitelline veins; b) the canal between the sinus 

 venosus and the ventricle, which, as the atrium develops at this 

 point, we may call the atrial canal; c) the common ventricle, 



Fig. 2 Model representing a cast of the cavities within the heart and the 

 connecting vessels in a rabbit embryo of nine days. Ventral view. Harvard 

 Embryological Collection, Series 619. 1, aortic branches; 2, right and left bulbs; 

 3, apertures formed by the septum dividing the bulboventricular canal; 4, 

 right shoulder; 5, left shoulder; 6, aperture formed by the septum dividing the 

 common ventricle; 7, atrial canal; 8, right vitelline vein; 9, left vitelline vein. 

 X 100. 



x The valuable study of the development of the pericardium in ferrets by 

 Professor Robinson (Journ. of Anat. and Phys., 1902, vol. 37) has recently been 

 extended by his pupil, Doctor Wang, with results which deserve more critical 

 consideration than can be given here. Being concerned especially with early 

 stages, Wang does not discuss the questions raised by Schulte, and his inter- 

 pretation of the model shown in figure 2 would differ from ours, as may be seen 

 by comparing it with his figure 31 representing the heart of a ferret of 13 to 14 

 segments. Wang's most interesting observation is of a 'primary heart rudiment,' 

 a vessel crossing the median line and subsequently dividing into two endothelial 

 tubes. The lateral vessels thus formed, or others somewhat posterior and lead- 

 ing to them, then reunite to make a 'secondary' heart. In the rabbits of the 

 Harvard Collection, as Doctor Lewis informs me, there may be seen a strand of 

 presumably angioblastic tissue in the region of the primary heart of Wang, but 

 nothing which should be interpreted as a heart. At present, therefore, we are 

 not inclined to recognize a heart previous to the union of the lateral cardiac 

 vessels. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 26, NO. 1 



