OF NON- VASCULAR ANIMAL TISSUES. 181 



sclerotic conjunctiva upon the cornea, from injections. The fine twigs of the arteries 

 of the sclerotic conjunctiva unite together around the margin of the cornea into a 

 vascular wreath or circle. From these there arise very numerous branches, which 

 run from the circumference towards the centre of the cornea, and in their course 

 make two or three subdivisions. Their ends bend distinctly inwards, and appear to 

 penetrate the proper substance of the cornea*." 



Mr. Tyrrell. " I have been thus satisfied that the vascular organization of the 

 cornea is principally derived from the conjunctiva, and little, if at all, from the scle- 

 rotic vessels -}~." 



Mr. Wardrop. " It (the cornea) is also nourished by the same vessels which sup- 

 ply the conjunctiva J." 



There is very considerable difficulty in making a complete injection of the vessels, 

 which have the function of supplying the cornea with a nutritive fluid §. 



The vascular system of the cornea resembles that of articular cartilage, in consist- 

 ing of two sets of vessels, one of which is devoted to the supply of its substance, and 

 which is in contact with its margin where it is attached to the sclerotic ; the other 

 supplies its free or mucous surface, the circumference of which it overlaps. 



In an eye which is injected with tolerable success, the white sclerotic membrane 

 will be observed to be traversed by two sets of vessels. One of these consists of 

 small and numerous branches, which have a straight direction towards the circum- 

 ference of the cornea. These are the ultimate branches of the sclerotic arteries which 

 course towards the cornea. The other set of vessels is composed of the large and 

 tortuous trunks which are seen with ease by the naked eye ; these are the sclerotic 

 veins, which take a retrograde course to the arteries just alluded to, and become 

 gradually larger as they get more remote from the cornea ; these sclerotic veins re- 

 turn the blood devoted to the nutrition of the cornea. 



Upon examining the arteries with a magnifying glass, they will be found, at the 

 circumference of the cornea, to terminate in two sets of vessels ; of these, one is 

 superficial, and consists of delicate branches which pass inwards over the surface of 

 the cornea, between it and its mucous covering, and are analogous to the vessels 

 of joints which pass between the articular cartilage and the synovial membrane. 

 The other set of vessels, in which the sclerotic arteries terminate, are much larger 

 than those just noticed, and are more like the continuation of their trunks ; these, at 

 the circumference of the cornea, pass into the substance of the sclerotic, where they 

 come in contact with the attached margin of the cornea. 



* Mr. Wharton Joxes, Medical Gazette, vol. xxiii, p. 593. 

 t Medical and Chirurgical Transactions, vol. xxi. p. 17- 

 X The Morbid Anatomy of the Human Eye. 



§ I have made more than fifty injections of the eye, and I possess only three specimens in which the vessels 

 alluded to are successfully filled. 



2 b2 



