Arterial Anomalies 7 
study of the branchial apparatus of different forms; he con- 
cluded, page 127: “ Bei allen Wirblethieren ohne Annahme kom- 
men in die fruhesten entwickelungszeit Anlagen zu einem Zungen- 
bein und Keimapparate vor.” 
v. Baer (1837), as the result of more extensive observations, 
revised his figure calling attention to the mistake he had made in 
interpretation of the carotids. The new figure was fig. 14, Plate 
IV, its general scheme is reproduced in fig. 2 of this study. A 
comparison of figs. 1 and 2 will show that his idea of the truncus 
arteriosus and carotids was changed, but he still believed that the 
subclavians arose from the third arch. 
Rathke (1843) criticized the last figure of v. Baer, calling par- 
ticular attention to the error in the origin of the subclavian ar- 
teries. In 1857 he issued his second work and figured the 
changes for the aortic arches in mammals on Plate VI, fig. 10; 
this I have copied as fig. 3. Aside from the point just referred 
to in his earlier work our principal interest in this figure is in the 
more detailed development of the carotids; he supposed that the 
basal portion of the third arch by elongation became the common 
carotids, and of the pulmonary arteries, he said, in speaking of 
the truncus arteriosus: “Es sendet nur einer von truncus (***) 
einen Zweig aus der sich Gableformig theilend auf beide Lungen 
ubergeht, und entwickelt sich darauf mit diesem Zweige und jenen 
erst erwahnten Canal zu der Lungenarterien, indass der andere 
funft Gefassbogen vergeht.” 
From the time of Rathke’s renowned precept of five pouches 
for the system of embryonal visceral arches the question of a 
greater number of arterial arches was not raised till van Bem- 
melen (1886) called attention to the presence in the embryos of 
reptiles and birds of a rudimentary vessel between the systemic 
and pulmonary arches. ‘This caused Boas (1888) to review the 
evidence of his earlier work (’81-’2—’6) calling attention to the 
origin of the pulmonary artery in amphibia and reptilia from the 
sixth arch. He concluded that the pulmonary artery arose from 
the corresponding arches in all vertebrates and that a true arch 
had been overlooked between the fourth and pulmonary arches. 
235 
