chap, i v.i THE ORBIT AND EYE. 45 



orbit for several days without the patient being 

 aware of it. A stranger case, ia some ways, is that 

 reported by Furneaux Jordan : " A man, who was 

 employed in threshing, became the subject of severe 

 ophthalmia. At the expiration of several weeks, the 

 patient, whilst pressing his finger on the lower eyelid, 

 suddenly ejected from a comfortable bed of warm pus 

 a grain, of wheat, which had shot forth a vigorous 

 green sprout." Tho orbital fat affords also an excel- 

 lent nidus for growing tumours. Fractures of the 

 inner wall of the orbit involving the nasal fossga or 

 sinuses, may lead to extensive emphysema of the orbital 

 cellular tissue. The air so introduced may cause the 

 globe to protrude, may limit its movements, may 

 spread to the lids, and will, in any case, be increased 

 in amount by blowing the nose, etc. 



The orbital muscles. The four recti muscles 

 end in thin, flat membranous tendons. The tendon 

 of the external or internal rectus muscle is frequently 

 divided for strabismus. The width of the tendons 

 varies from 7 mm. to 9 mm. They are inserted into 

 the sclerotic near the cornea. The internal rectus is 

 inserted 6'5 mm. from the corneal margin, the ex- 

 ternal 6 '8 mm., the inferior 7 '2 mm., and the superior 

 8 mm. (Merkel). 



The external and inferior recti are the longest, 

 the internal rectus is the broadest, and the superior ia 

 the narrowest and slightest. 



The orbital arteries are small, and seldom give 

 rise to trouble when divided in excising the globe, 

 since they can be readily compressed against the bony 

 walls of the cavity. Pulsating tumours of this part, 

 may be due to traumatic aneurisms of one of the 

 orbital arteries, or may depend upon an arterio- venous 

 aneurism formed between the internal carotid artery 

 and the cavernous sinus. Pressure also upon the 

 ophthalmic vein (as it enters the sinus), by an aneurism 



