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HENRY A. MURRAY, JR. 



some conditions are to be recommended. For the finer details, 

 however, thin sections are naturally the more desirable. The 

 embryos were variously stained. My observations lead me to 

 believe that the development of the rabbit heart tallies in every 

 important respect with that of the cat. 



In the accompanying diagram (fig. 1), the schema usually 

 presented to portray the formation of the cardiac loop may be 

 contrasted with a parallel series of figures representing Doctor 

 Schulte's findings. Note that the initial and final stages in each 



A 



B 



Fig. 1 A. Schema of cardiac loop formation; as presented in most modern 

 text-books, based on the His models. B. Schema representing the same period 

 of development, as observed by Doctor Schulte in the Columbia Laboratory. 

 (Note that the bulboventricular clefts are formed in both hearts before fusion 

 takes place, that the left groove together with the left shoulder of the ventricle 

 becomes accentuated, that there is a corresponding obliteration of the right 

 groove and shoulder, and that the venous end of the heart migrates to the left. 

 These are the principal factors in the formation of the loop.) 



case are the same, but that the intervening processes are dis- 

 similar. Instead of reiterating Doctor Hchulte's conclusions, I 

 will ask the reader to examine carefully figure 2 before reading 

 the following explanation. It is a model of the endocardial 

 cavity in a nine-day rabbit. The myocardial mantles, not repre- 

 sented in the model, have completely fused, but the endothelial 

 tubes have not as yet entirely coalesced. The picture presents 

 a condition previous to the complete amalgamation of the vessels 

 to form a common cavity. Those points where the endocardia 



