ARTERIES OF BIRDS. 191 



In the following details of the vascular system, I adopt, with 

 little modification, the words of Macartney, by whom it was 

 first and best described in his Article * Birds,' in ^ Rees's Cyclo- 

 paedia.' The carotid artery emerges from between the muscles 

 of the neck, at about the third or fourth vertebra from the head 

 (9); and after giving off the arteries, cutanece colli later ales, fig. 

 93, 10, 11, to the lateral muscles and integuments of the neck, it 

 runs along the outer edge of the rectus major anticus to behind 

 the angle of the jaw, Avhere it divides into its several branches. 



An artery {arteria occipitalis) first goes off posteriorly, which 

 passes a little forward under the thyrohyal, and after sending 

 some blood to the muscles of the neck, makes a turn backward, 

 enters the foramen in the transverse process of the second ver- 

 tebra, and terminates by anastomosing mth the vertebral artery.* 



The next branch is the entocarotid ; it passes behind the 

 muscles of the jaw close to the basioccipital, sends a branch 

 upward, which penetrates the tympanum ; and another througli 

 the articulation of the jaw, to unite with the ophthalmic, and con- 

 tribute to the plexus at the back of the orbit (rete ophtlialmicum 

 of Barkow). The entocarotid then enters an osseous canal, which 

 runs along the side of the basisphenoid between the tables of the 

 bone ; and at the lower and back part of the orbit, the artery 

 receives a remarkable anastomosing branch of the internal maxil- 

 lary, which almost equals in size the carotid itself, and these two 

 vessels produce by their union one which passes almost directly 

 to the cranium, entering at the deep ' sella turcica.' It forms 

 within the skull an anastomosis similar to the circle of Willis ; but 

 the branch which occupies the place of the basilar artery is very 

 small, and appears to be furnished entirely from the anastomosis 

 of the carotids, and designed only to supply the medulla oblon- 

 gata. The branches of the entocarotid are spread in an arbo- 

 rescent form upon the surfaces of the brain ; some on the outside 

 and others on the ventricles and the fissure between the two 

 hemispheres : the tufted termination of the vessels of the choroid 

 plexus is shown in fig. 46. The orbital plexus formed by the 

 carotid sends off the inferior palpehral, ethmoidal, lacrymal, and 

 ophthalmic arteries. The ophthalmic artery forms two remarkable 

 plexuses at the posterior part of the globe of the eye ; the first, 

 fig. 59, s, is situated close beside the inner side of the optic nerve, 

 is formed by an artery answering to the arteria centralis retincB, 



' Barkow, xliv., has established the accuracy of this observ^ation of Macartney's 

 (xLiu-.), having found this singular anastomosis of the occipital with the vertebral 

 artery in all the birds which he injected. 



