CONTENTS
PAGE
Introduction [555]
Methods and Materials [556]
Myology and Angiology: Hirundinidae [557]
Myology [557]
Angiology [558]
Myology and Angiology: Columbidae [560]
Myology [560]
Angiology [560]
Summary of Arterial Arrangement [562]
Discussion and Conclusions [562]
Individual Variation [562]
Intrafamilial Differences [563]
Interfamilial Differences [565]
Summary [567]
Literature Cited [573]
INTRODUCTION
Most descriptions of the circulatory system of birds, largely the work of Glenny, have dealt with arteries of the neck and thorax in a wide variety of species. As a result of his work, Glenny offered several hypotheses concerning the phylogenetic, hence taxonomic, significance of differences in some of these vessels. He also described six types of thoracic arterial arrangements and stated that these categories might represent various levels of evolution (Glenny, 1955:543-544).
The families Columbidae (pigeons) and Hirundinidae (swallows) have two nearly extreme arterial types described by Glenny, and are universally acknowledged as monophyletic. Differences within the families, therefore, can be considered as valid intrafamilial differences. I have investigated the thoracic and coracoid arteries and their branches in members of these two families to determine the degree of individual variability of the vessels, and the possible causes of interspecific and intrafamilial differences.