55 THE RABBIT CHAP. 



Insert the handle of a scalpel between the iris and sclerotic and 

 separate off the latter from the choroid around the outer half of the eye- 

 ball, first making four radial cuts in the sclerotic, beginning at its 

 margin, at equal distances from one another. Turn back the four flaps 

 thus made, and insert pins through them so as to fix the eye firmly 

 down under water with the iris uppermost : note the ciliary muscle around 

 the outer margin of the iris, the choroid , and the ciliary vessels and 

 nerves. Then make two radial cuts, a short distance from one another, 

 through the iris, and turn back the portion between the cuts, noting the 

 ciliary processes. Sketch. 



Cut through the choroid and the parts enclosed by it, horizontally, 

 around the line up to which it has been already exposed, so as to 

 separate the eyeball into an inner and outer hemisphere : in doing so, 

 the gelatinous vitreotis humour must be cut with the scissors. Examine 

 and sketch both sections, noting in the outer hemisphere the retina, 

 stopping short at the outer margin of the ciliary processes, and the lens 

 with its capstde ; and in the inner hemisphere the retina with its blood- 

 vessels, and the blind-spot (or point of entrance of the optic nerve). 

 Then remove the retina and observe the choroid with its iridescent 

 tapetum. 



2. Cut your second specimen into vertical halves with the scissors, 

 making the cut pass through the cornea, pupil, and optic nerve. As it 

 is difficult to cut through the lens without disturbing its relations, it 

 should be carefully separated from one half, and left entire on the other 

 half. Examine the relations of the parts once more, compare Fig. 57, 

 and sketch. 



I- Dissection of typical flexor and extensor muscles and 

 joints of the fore -limb. 



1. Expose the biceps (chief flexor of the fore-arm). Its origin is 

 from the anterior edge of the glenoid cavity on the pectoral arch : it 

 arises by a single long tendon, working in the bicipital groove of the 

 humerus. It is spindle-shaped, consisting of a single belly, and is 

 inserted on the proximal end of the radius. 



2. Expose the triceps (chief extensor of the fore-arm). It arises 

 by three main heads from the pectoral arch and humerus, and is inserted 

 on the olecranon-process of the ulna. 



3. Remove the muscles from the shoulder-joint, and note the 

 capsular ligament (p. 55). Cut through this so as to open the svnovial 



