VEINS OF THE CHOROID. 329 



The plexiform character of this vascular circle is not equally 

 well marked in all eyes ; it occurs especially in those parts of 

 the circumference where the veins proceeding from the ciliary 

 muscle join it. These pass at the anterior extremity of the muscle 

 to the internal surface of the sclerotic (in one case I counted from 

 twelve to fourteen of them), divide near the venous circle 

 into several anastomosing branches, which partly perforate the 

 sclerotic obliquely, in order to join with the episcleral venous 

 plexus (see below) and the veins of the recti muscles, and 

 partly enter the circulus venosus itself. At these points the 

 latter often appears to be dilated, whilst it is prolonged directly 

 into the plexus of the veins emerging from the ciliary muscle, 

 or forms itself a circular venous plexus. 



Moreover in vertical sections made in the region of the mar- 

 gin of the cornea, especially in injected specimens, we almosi) 

 always find, besides the single large vascular lumen, one or 

 more smaller ones, or we may meet with two or more lumina, 

 which not unfrequently anastomose with each other. 



The venous circle of Schlemm appears to constitute a kind 

 of reservoir for the blood of the ciliary muscle in the varying 

 conditions of its contractions. The position of the channel in 

 regard to the muscle is such that the contraction of the latter 

 may occasion a dilatation of the vessels forming it. 



In most animals a circular venous plexus occurs at the same 

 point. (Rouget, G. Meyer, IwanofT, and Rollett.) 



In the preceding description I trust I have avoided the 

 objection raised by Henle* to my former account, that I laid 

 too much stress upon the plexiform character of the circulus 

 venosus. I certainly never thought, as Henle appears to 

 believe,t that the circle is always composed of a large number 

 of small vessels. The confounding of the circulus venosus 

 with the so-called canal of Fontana (which is present in the Ox, 

 but not in Man), formerly led to great confusion, which has 

 recently been revived by Pelechin,| but the distinction between 



* Jahresbericht iiber d. Fortschritte der Anatomie fur 1865, Zeitschrift fur 

 rat. Med., Ser. iii., Band xxvii., pp. 96 and 97. 



f Handbuch der Anatomie, Band iii., Heft i. (Gefdsskhre), p. 344, note. 

 J Ueber den sogenannte Kanal von Fontana oder Schlemm (On the so- 



