to
which vessels they are referring. Fisher (1955:287-288) found
variability in the Whooping Crane, _Grus americana_, of the axillary,
coracoid, thoracic, and pectoral arteries. In one specimen he found
these vessels arising on the right side from the subclavian, in the
sequence just listed, and on the left side all arose from the same
point. Berger (1956:439-440) strongly emphasized the variability of the
vascular system, calling it the most variable in the body. As he stated,
this high degree of individual variation seems to be due to the
embryological development of the system, wherein many of the adult
channels of circulation are derived from embryonic plexuses.

Intrafamilial Differences

In spite of the rather extensive amount of individual variability in
some vessels, I found the over-all pattern of arteries to be relatively
constant within the family Columbidae and within the family
Hirundinidae. There are, nevertheless, several intrafamilial differences
needing some further discussion and clarification.

Others have reported the occasional presence of more than one coracoid
artery on each side in some columbids, these arteries being described as
arising from various sites and being variously named. Bhaduri and Biswas
(1954) described the arterial situation in seven species of the family
Columbidae (_Columba livia_, _Streptopelia tranquebarica_, _S.
chinensis_, _S. senegalensis_, _Chalcophaps indica_, _Treron bicincta_,
and _T. phoenicoptera_) and stated (_op. cit._: 348) that "The
sternoclavicular [= coracoid] artery is similar in all the species, but
the domestic pigeon seems to be unique in that it has, in addition, a
small vessel, the accessory sternoclavicular." This artery was described
later, in the domestic pigeon, as follows (Bhaduri, Biswas, and Das,
1957:5): "A minute and insignificant vessel which has been termed the
_accessory sternoclavicular_ artery... is given off close to the origin
of the sternoclavicular. It passes anteroventrally to supply the
adjacent muscles." Glenny (1955:577) described the arterial pattern
characteristic of members of the family Columbidae (more than 30 species
studied by him) and stated that "three pairs of coracoid arteries are
found in _Otidiphaps nobilis_, normally one or two pairs may be found."
As suggested by Bhaduri and Biswas (1954:348), the "accessory" vessel
probably corresponds to a vessel previously described by Glenny (1940)
in _Streptopelia chinensis_