ANGEIOLOGY. 85 



far as the ciliary circle, wliere they subdivide ; 6, muscular arteries to the 

 different muscles in the orbit ; 7, ethmoidal^ to the mucous membrane in the 

 ethmoidal cells ; 8, superior and inferior jialpehral to the palpebral, caruncula, 

 conjunctiva, and lachrymal sac ; 9, nasal^ to the side of the nose; 10, fron- 

 tal^ to the eyebrow and forehead. 



The posterior communicans arises from the carotid opposite to the 

 ophthalmic, passes backwards and inwards, and joins the posterior cerebral 

 circle. 



The anterior cerebri, or arteria callosa, passes forwards and inwards above 

 the optic nerve, anastomosing with the opposite by a short transverse branch, 

 the anterior communicans, and ultimately terminates by dividing into 

 branches for the corresponding hemisphere of the cerebrum. 



The media cerebri, or middle cerebral artery, passes outwards in the fissure 

 of Sylvius, and divides into two tortuous branches which supply the anterior 

 and middle lobes of the cerebrum, sinking deep in the sulci between the 

 convolutions in the island of Eeil. ' 



PL 135, ßg. 5, distribution of the ophthalmic artery : ', superior dental J 

 *, inferior dental ; % internal carotid ; *, ophthalmic artery ; ^, muscular 

 branches ; ', lachrymal ; ', supra-orbital ; % frontal artery ; *, a short or 

 posterior ciliary; "*, a long ciliary; "■ ", ethmoidal; ", frontal branch. 

 Fig. 6, some of the deep branches of the ophthalmic, the eyeball removed : 

 ', ophthalmic ; °, artery of the lachrymal sac ; ', superior, and ', inferior 

 palpebrae. Fig. 7, cerebral arteries : ', anterior ; '", middle lobe of the 

 cerebrum ; \ fissure of Sylvius ; ', pons varolii ; ', cerebellum ; % medulla 

 oblongata ; ', section of the trunk of the internal carotid ; *, posterior com- 

 municans ; *', choroid artery ; '", artery of the corpus callosum ; ", anterior 

 communicans. 



C The Subclavian Arteries and their continuations. 



The great arterial trunks, of which the subclavian constitute the initial 

 portion, have different names in different parts of their course, the series 

 consisting of the subclavian proper, the axillary, the brachial, and the radiaf 

 and ulnar. 



1. The SuBCLAViAi^' Arteries Proper. The right and left subclavian 

 arteries differ in diameter, length, situation, and relation. The right, as 

 arising from the innominata, is shorter than the left, which springs from the 

 arch of the aorta. The course of each may be divided into three stages : 

 the first extends from the origin to the tracheal edge of the scalenus anti- 

 cus ; the middle stage is the transit of the artery between the scaleni mus- 

 cles ; the third stage extends from those muscles beneath the clavicle to the 

 lower border of the first rib, below which the continued trunk receives the 

 name of axillary arter3\ In the middle and last stages the right and left 

 arteries are similarly circumstanced in all respects ; the first stage is much 

 longer on the left than on the right side. 



The right subclavian, in its first stage, passes outwards and a little 

 upwards, having anterior to it the internal jugular and subclavian veins, 

 the sterno-mastoid, hyoid, and thyroid muscles. The left subclavian, from 



791 



