2 ' C. W. M. Poynter 



ances. One paper relating to the aortic arches has already ap- 

 peared, Poynter (1916), and in this one I shall confine myself 

 to the anomalies of the heart. There are few subjects which 

 have attracted more attention among the medical profession than 

 the irregularities in the development of the heart and great ves- 

 sels, but in the case of the heart the interest is not so much from 

 the teratological side as in the case of the arteries; its develop- 

 mental defects are frequently of such serious consequence to the 

 life of the individual as to command the attention of the clinician 

 and pathologist, with the result, that these cases have been studied 

 as a pathological problem rather than an embryological one. 



I had first intended to report the cases I have had the oppor- 

 tunity of studying, but as my bibliography has grown there has 

 seemed to be no profit in adding more examples to those already 

 reported, since I have observed no new conditions or complexes. 

 In the earlier study it was frequently difficult to find the literature 

 relating to any specific lesion, consequently I have included a full 

 literature list so that the cases which appear as a basis for this 

 study may be readily available to any one desiring to consult 

 them. 



Etiology. — The etiology of malformations of the heart cannot 

 be any more definitely stated than that of any other develop- 

 mental anomaly. Experimental research has taught us that if 

 the normal developmental conditions are interfered with anoma- 

 lies will result. Such anomalies are not confined to any anatom- 

 ical system and vary in degree or extent depending on the time 

 and intensity of the action and, no doubt, on other factors as well. 

 Dareste has been able to produce a wide variety of anomalies by 

 varying the temperature of the incubator during the development 

 of the chick, and other investigators have been equally successful 

 with fishes by growing them in various chemical solutions. 

 Many hybrids develop irregularly and the proper application of 

 the X-ray will produce growth disturbances. I have produced a 

 wide variety of the recorded anomalies by incubating chick eggs 

 then subjecting them to a temperature near freezing for a time 

 before continuing the incubation. It would seem that the only, 

 or principal, action of the cold is to inhibit oxidation and so dis- 



