DK. J. MUEIE ON THE ANATOMY OP THE SEA-LION. 535 



posteriorly, and about ■£$ of an inch wide. The fibres are not perfectly circular, but 

 are seen to be derived from the radii of the dilator, and as they approach the pupil to 

 interlace and proceed to the edge obliquely. The ciliary muscle is well developed. 

 The venous meshwork constituting the canal of Schlem has considerable volume. 

 The ciliary processes of the iris are between 90 and 100 in number. The crystalline 

 lens, half an inch in diameter, is nearly spherical or with a very limited antero-posterior 

 flattening. The capsule and suspensory ligament are both strong and well developed. 

 The optic nerve pierces the eyeball 0*2 inch below its centre. 



b. Orbital Muscles. — Of these a retractor, or what may represent the levator palpebrse 

 and tensor tarsi, is a broadish thin sheet in intimate union with the superior rectus ; 

 it separates at the fore part of the eyeball, passes over the superior oblique, and then 

 is lost among the circular fibres of the orbicularis palpebrarum. A few of its fasciculi 

 join with the superior oblique and internal rectus. Four recti are present; and, as 

 usual, the obliqui are two in number. The superior one of these is of moderate 

 size, wanting in tendon and pulley, and fleshy almost to its ocular termination. It runs 

 obliquely, as a broad band enclosed anteriorly between the rectus superior and 

 palpebral retractor ; it then turns downwards, outwards, and forwards, to be inserted 

 into the middle of the eyeball. At the latter attachment it is overridden by the in- 

 ternal rectus, while it covers a slip of the choanoid muscle. The inferior oblique is 

 thin and narrow, it is fixed into the globes of the eye, ^ of an inch below the superior 

 oblique. The choanoid or retractor oculi muscle is split into four unequal-sized 

 segments. The internal inferior one of these is the most delicate and separated slip. 

 Its insertion is below the inferior oblique muscle, just behind it and the lobes of the 

 Harderian gland. The upper inner slip is slightly thicker than the former ; it passes 

 to the back of the globe, and behind the insertion of the superior oblique muscle. The 

 two outer portions are much broader muscular sheets, and together in close approxi- 

 mation cover the globe for a third of its posterior circumference. 



IV. The Vascular System. 

 1. Cardiac Receptacle. 

 When the muscular organ of the heart is fully distended, or, say, filled with plaster 

 of Paris, it appears to be of great proportional bulk to the body ; more especially both 

 auricles and the right ventricular cavity seem unusually large and protuberant. In the 

 flaccid condition it is only of moderate dimensions, namely 6^ inches in longitudinal, 

 and 5 inches in transverse diameter. The left ventricle measures 5 inches from its root 

 to the apex. The form of the heart as a whole is flat, broad, and obtusely pointed, 

 the apex, indeed, presenting a tendency to bifurcation. The median longitudinal and 

 auricular furrows are shallow. The strong fibrous pericardial investment is attached to 

 the aorta, 2 inches above its root on the right side, but considerably lower on the left. 



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