Arterial Anomalies 25 
is due to stretching; this stretching occurs through the force of 
the left pulmonary artery being filled with blood. Stienon (1912) 
recognized the changed relations dependent on the establishment 
of the pulmonary circulation but thought that the ductus also be- 
comes compressed by the expanding left lung. 
Taking into consideration then the three theories of closure, 
1, €., decreased blood pressure, absence of muscular fibers in the 
wall of the ductus and mechanical influences, a study of the cases 
in which the ductus remains open would suggest that more fre- 
quently a condition of pressure in the vessels, similar to that exist- 
ing before birth, is the most important element although no doubt 
the other factors, or rather the disturbance of their action, may 
have an influence. 
As indicated above the factors producing situs transversus and 
right aortic arch seem to have little influence on the development 
of the pulmonic arch and in these conditions when the ductus per- 
sists it may join the descending aorta, Dubrueil (1847), Chartier 
(1905 ),—or it may open into the left subclavian when that vesset 
is the last branch of the arch. This condition should not be con- 
fused with double aortic arch, for in both there is a vascular ring 
about the trachea and esophagus. 
The following cases illustrate the union of the ductus with the 
left subclavian artery when it is the last branch of the arch: 
Klinkosch (1766), Cailliot (1807), Obet (1808), Bernhard (1818), Her- 
mann (1830), Ewen (1840), Greig (1852), Fick (1854), Tiingel (1862), 
Broader (1866), Cameron (1871), Combes & Christopherson (1884), Lane 
(1887), Riche (1897), Garnier & Villemin (1909). 
Persistence of the left arch, ductus arteriosus Botalli, is not a 
wide departure from the normal and cases with or without other 
developmental anomalies in conjunction are numerous. Varia- 
tion in the position of the distal end presents a point of some in- 
terest. Normally during development when the arch is formed 
it is joined to the dorsal aorta at a point slightly above the defini- 
tive subclavian artery; later in the adjustment of parts it is fre- 
quently found below the subclavian origin. It would seem thai 
there has been a disturbance of the normal shifting process in 
those cases in which the ductus joins the subclavian artery instead 
253 
