THE EYE AND ITS APPENDAGES 119 



The cartilage should first be manipulated to ascertain whether 

 there are any abnormal adhesions. Having done this, the head of the 

 patient should be held as still as possible whilst the operator passes a 

 curved, threaded needle through the cartilage. The needle should be 

 held with its convexity directed towards the eyeball, and it should be 

 passed through the cartilage from within outwards. Having thus 

 secured the cartilage it is then drawn out as far as possible, and with 

 a curved pair of scissors, its posterior extremity should be severed 

 from its attachment. 



The Lachrymal Canals. — These are found in the eyelids themselves, 

 and they are lined by a continuation of the conjunctiva. 



They open separately into a membranous receptacle called the 

 lachrymal sac, which is placed in the lachrymal fossa on the floor of 

 the orbit. The sac in turn discharges its contents into the ductus ad 

 nasum or lachrymal duct. The latter is a long membranous tube 

 which runs at first along the osseous canal on the inner aspect of the 

 lachrymal and superior maxillary bones, to open on the floor of the 

 nasal cavity. The inferior opening is easily seen in the living animal 

 by separating the alx of the nostril. It appears as though a small 

 circular piece of skin had been punched out. Its position is in the 

 skin immediately in front of the line of division between the skin 

 and mucous membrane. To reach this spot from the osseous canal 

 mentioned the duct passes beneath the mucous membrane lining the 

 middle meatus of the nasal chamber. 



Epiphora. — This is the name technically given to the condition 

 resulting from an obstruction of the ductus ad nasum. 



It will be easily understood that the first symptom will be an 

 overflow of the lachrymal fluid. The obstruction may be placed 

 anywhere along the course of the duct, and the first step necessary 

 is to discover as near as possible its position. This may be done by 

 means of injections into the duct, and it is stated that if the injection 

 escapes chiefly through the upper opening, the obstruction is not far 



