DEVELOPMENT OF VESSELS WITHOUT HEART 



197 



chicks that were opened before the heart had formed. This 

 operation was often successful, while at other times the heart 

 would later be found developing out in the area pellucida, sepa- 

 rate and apart from the embryo or connected with it by a few 

 capillaries. Figure 17 is a case of this kind. The small vesicle 

 shown was pulsating at a normal rate when the egg was opened. 

 By its dilatation blood was sucked in and with its contraction 

 the blood was discharged again into the capillaries, the blood 



Fig. 17 A free-hand drawing of a chick in which the heart had not been de- 

 stroyed, but developed out in the area pellucida. The appearance of the capil- 

 laries through which the feeble circulation flowed is illustrated. Incubated 3 

 days. 



cells moving back and forth over about the same distance each 

 time. That this process had some effect upon the formation of 

 the capillaries directly connected with them is apparent from 

 their radial arrangement as compared with adjoining capillaries 

 to which the circulation did not extend. 



After a similar operation, I found a pulsating vesicle in the 

 area opaca very close to the sinus terminalis although not con- 

 nected with the border vein. This vesicle was connected with 

 a relatively huge blood vessel which extended parallel to the 

 sinus terminalis for a short distance and then broke up into 

 radial capillaries through which ink injected into the large vessel 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 1 



