6 C. W. M. Poynter 
SIRO sla AON, NIRCIBUSS) 
The earliest observations on the aortic arches were made on 
birds; Haller (1758) recognized a stage in the chick when there 
were three vessels and this was antedated by the work of Mal- 
pighi who figured three arches. Pander (1817), in Tab. IX, fig. 
3, showed three arches in a three-day chick; these figures are 
possibly copied from Malpighi, he recognized that early there 
were two dorsal aortae. v. Baer (1827) also saw two dorsal ar- 
teries, saying that about the fortieth hour the blood was forced 
around the gut in two trunks; these proceed on each side under 
the vertebral column, probably uniting after having been separate 
for a considerable distance. Serres (1830) saw between the for- 
tieth and fiftieth hours a double aorta throughout its entire length; 
he affirmed that the single aorta was formed by the gradual fusion 
of these two trunks. He does not however seem to have had a 
clear conception of the branchial arteries. 
Rusconi (1817) comprehended the formation of the arterial 
stems from the vessels of the visceral arches and described the 
metamorphosis from the fish type for salamander. This work 
was followed by that of Huschke (1817) and v. Baer (1827) for 
birds, and v. Baer (1828) for mammals. 
Rathke is quite generally credited with originating the diagram- 
matic figures illustrating the fate of the aortic arches, but I be- 
lieve the first figure of this kind was made by v. Baer (1828) as 
fig. 3, Plate IV ; see fig. 1 of this study. This figure was referred 
to by him in his discussion of both birds and mammals and in 
that discussion he clearly indicates that the right arch persists in 
birds while in mammals the left remains. As noted in fig. 1 this 
is a left arch. Thomson (1830. copied the figure as a right arch 
and introduced a second figure of a left arch which he referred to 
as representing the mammalian condition. 
_ v. Baer (1828) clearly understood the phylogenetic significance 
of the aortic arches, for he said, page 518: “ Die erste Bildung 
des Arterien Systems wird aber durch die Halskeimen auf eine 
bei allen Wirbelthieren, bei den Fischen bleibend, bei den hoheren 
Classen vorubergehend.” Rathke (1832) made an exhaustive 
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