OCR Text |
Show 1873.] MR. GARROD ON THE CAROTID ARTERIES OF BIRDS. 457 linago is the only genus which produces peculiar intertropical species. All the other generic forms met with in the tropics of the New World are represented (as in the case of Tringa, Numenius, Mgialites) by arctic species descending south. Antarctic America, however, has some indigenous generic forms, such as Oreo-philus, Phegornis, and Pluvianellus, and a few peculiar species of genera of wide distribution. 4. On the Carotid Arteries of Birds. By A. H . G A R R O D , B.A., F.Z.S., Prosector to the Society. [Eeceived April 10, 1873.] Between the years 1825 and 1830 three anatomists published the results of their independent observations respecting the number of and the variations in the carotid arteries of the different members of the class Aves. The first of these was Bauer*, who, in 1825, pointed out some of the most noteworthy peculiarities, which have been subsequently verified. Meckel f, in 1826, was enabled to demonstrate the existence of other marked variations; and his observations, extending over a considerable period, are incorporated in his 'Comparative Anatomy.' In 1829, C. L. Nitzsch selected the same subject for a disquisition before the University of HalleJ. Since that time scarcely any further additions have been made, and the subject has been almost entirely neglected. It is not easy to understand the reason of this; for it is generally acknowledged that what bas been already done by tbe above-named authors is extremely valuable as an assistance towards a knowledge of the correct classification of birds, and yet they have left much for other workers in the same field. The opportunities afforded m e by this Society, as their Prosector, and by many kind friends, who have supplied me with specimens, in spirit, of genera and species otherwise unobtainable, have enabled me to collect together a sufficient number of facts, previously unrecorded, to make me feel justified in presenting to this Society a fresh list, in which is recorded the arrangement of the carotids of the various birds examined by myself, at the same time that the previously known results of Bauer, Meckel, and Nitzsch, and a few others, are incorporated in the general statements. In birds, the aorta, immediately after it has sprung from the heart, divides, as stated by Meckel, and contrary to the opinion of Cuvier, into two branches, the left innominate and the continuation of the main trunk. This latter again almost immediately divides into the right innominate and the descending aortic arch. Each innominate, after sending off pectoral and subclavian branches, continues to ascend a short way ; and when near the superior aperture * Disquis. circa nonnullarum Avium systema arteriosum (Berol. 1825). f ". Beitrag zur Geschichtc des Gefass-Syst. der Vogel," Meckel's Archiv, 1826. j Observationes de Avium arteria carotide communi (Hala:, 1829). |