46 FRANKLIN P. REAGAN 



ence to the possibility that non-continuous vascular lumina 

 exist. Huntington and McClure have repeatedly called atten- 

 tion to the fact that injection will do nothing more than demon- 

 strate continuous cavities. Those who believe the injection 

 method to be adequate, maintain that any cavity in the unin- 

 jectible periphery is necessarily a non- vascular cavity or an 

 artifact. In case of the early vessels in the chick, the injection 

 method should be able to demonstrate all endothelium from the 

 moment that the independently formed portions of the angio- 

 blast or 'unit anlage' have become confluent. In this connec- 

 tion Schulte (63, p. 25) states: 



From this moment .... there is a sudden and abrupt end to 

 the production of discrete anlages, contrary to what one would expect 

 from the general transitions in natural processes. 



But in view of the many anlages admittedl}' present in the splanchno- 

 pleure and in the embryo, and of transitions almost universally observed 

 in natural processes, the possibility must be conceded that a belated 

 vesicle or two of endotheliimi might conceivably escape a sudden 

 annexation to the injectible system. It becomes of interest to deter- 

 mine its status affer injection has been practised and it has failed 

 hypothetically to be injected. A moment before, had it been observed 

 in vitro, or had it been sectioned, it would have appeared like an}^ other 

 of the discrete anlages in the 'anlage.' But the test of injection made, 

 it at once ceases to have a future, it has become an artifact, or if perti- 

 naciously insisted upon, a Mayer-Lewis anlage. Because .... 

 it failed of concrescence prior to the moment of injection it is abso- 

 lutely devoid of vascular potentialities and could never, had the injec- 

 tion been omitted, have joined its fellows and participated in the for- 

 mation of the vascular system (p- 7). We may recognize, 



or refuse to recognize the uninjectible periphery. If we recognize it, 

 the method of injection becomes not only partial and incomplete, but 

 subordinate to the methods which reveal all its findings and in addi- 

 tion, enlarge our field of observation. 



. . . . (p. 27). To ... . insist that the limited field ex- 

 plored by injection is alone accessible to investigation is not to assert 

 the primacy of the injection method, but to fall back upon an ancient 



logical device known as -petitio principii (p. 26). There 



is, however, no reason to assmne that injection has reached the acme 

 of delicacy, great as is the skill which has been developed in its use. 

 It is conceivable that some day it will be possible to inject a portion of 

 the 'anlage' before its admittedly discrete vessels have fused — even a 

 small fragment might be injected alone, the dorsal aorta in the head, 

 say, or the umbilical vein. This would then become to the injectionist 

 the only source of the vascular system. The uninjected parts of the 



