ORIGIN OF VASCULAR TISSUES 49 



merit of the vascular system as given in Keibel and Mall's 

 Human Embryology, 1912, probably represents the consensus of 

 opinion among the majority of American and European anat- 

 omists up to 1913 — namely that the vascular tissues were of 

 angioblastic origin. A thorough survey of the literature and 

 most recent text books does not lead one to agree with Stockard 

 (66, p. 587) that the recent defenses (Stockard considers them 

 'revivals') of the ingrowth theory were prompted by purely 

 'literary reasons.' Also it is improbable that we have reached 

 the era in which philosophical questions can be divorced from 

 the interpretations of the results reached by our methods. 



It may well be said that the thirtieth session of the American 

 Association of Anatomists, 1913, marks a new epoch in the 

 endothelium controversy. Schulte at that time showed that 

 the anlagen of the umbilical vein develop locally from parietal 

 mesoderm entirely away from splanchnopleuric vascular anlagen. 

 McClure showed that an isolated lymphatic anhge could be 

 injected directly and independently. But in addition to these 

 significant morphological contributions there stands out in im- 

 portance the experimental work of Miller and McWhorter (40) 

 who had obtained blood-vessels on the operated sides of chick 

 embryos, one side of which had been excised from the yolk-sac 

 blastoderm. This work is not the first experimental investiga- 

 tion of the problem, but it marks a revival of that sort of investi- 

 gation of endothelium; it marks the beginning of a serious appre- 

 ciation of such work, and a concession on the part of many 

 anatomists that the local origin theory is not a priori untenable. 



As already stated, the work of Miller and McWhorter was 

 not the first attempt to utilize the experimental method in the 

 solution of problems having to do with the origin of the vascu- 

 lar tissues. In the year 1887 there were three experimental 

 investigations bearing on such problems — the investigations of 

 Budge, Gerlach, and Uskow. 



Budge (5) proposed to confirm the view of His by destroying 

 the germinal disc of unincubated eggs, leaving the germ- walls 

 intact so that the latter might demonstrate its independence as 

 the source of the vascular tissue. Gerlach (14) tried to deter- 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 21, NO. 1 



