After the lacrimal gland has been dissected away, a beginning will have been made for cutting away the fat and the connective tissue. The first thing to do then is to locate the superior oblique muscle. Try to keep track of which part of the eye is the inner side. Having located the inner side, feel along the top for a little hard eminence. That is the pulley. Begin to dissect around the pulley, not through it, and then follow the muscle along to its origin; do not separate the muscle from its origin. When the superior oblique is completely freed, the action of the muscle may be readily demonstrated by holding the “ring” or tendinous pulley with the fingers of one hand, while the muscle is pulled backward and forward with the other. THE OTHER EXTRINSIC MUSCLES With the dissection of Tenon’s capsule and the superior oblique muscle, the work of isolating the other extrinsic muscles will have begun. This work needs no directions except a warning to be careful not to injure the pulley of the superior oblique, and to be careful not to cut away the inferior oblique. The inferior oblique will be found to be near the “pulley.” If the dissection is not carried too close to the origin of the recti muscles, all the muscles may be kept in place. If the eye has not been previously subjected to the hardening influence of formaldehyde, it may be put into a 5 per cent. solution, and at the end of ten or twelve hours the muscles will have become rigid. They can then be better studied, and may be kept indefinitely. (Fig. 60.) [Illustration: Fig. 60--Showing the tendinous pulley of the superior oblique muscle and the extrinsic muscles.] THE THREE TUNICS OF THE EYE, THE HYALOID AND ITS ATTACHMENTS This dissection is a rather difficult one to make, and requires patience. [Illustration: Fig. 61--Cutting through the iris.] Prepare an eye by placing it in a 5 per cent. solution of formaldehyde for about ten days to two weeks. Remove all the outside tissues. Cut away the cornea, as in the dissection for the choroid or the retina. Loosen, as far back as possible, the sclerotic from the choroid. Remove the sclerotic for about 10 mm. back of the equator of the eye. With the tweezers pick up the pupillary edge of the iris. Using the small pointed scissors, cut through the iris. (Fig. 61.) Lift either one of the cut edges of the iris, and, with the sharp edge of the scalpel, gently scrape the _processus zonuloe_ free from the ciliary processes, cutting through the ciliary ring as the ciliary processes are detached from the hyaloid (_processus zonuloe_). (Fig. 62.) [Illustration: Fig. 62--Scraping the ciliary processes free. Showing, also, the choroid cut around the ciliary ring.] Great care must be taken not to thrust the point of the scissors into the hyaloid, suspensory ligament, or vitreous, else the lens may become detached.