210 DISEASES DUE TO INTERNAL PAEABITES. 



iiess, and stagger, but they do not turn in a circle or show evi- 

 dences of any acute brain disturbance, all signs tending to show 

 an obstruction and irritation of the nasal chambers. 



The duration of the attack may be from sixty days to ten 

 months, all depending on the time the larvae remain in the nasal 

 chambers. A sheep may be re-infected at different times, and 

 so contain larvae of different sizes and various stages of develop- 

 ment. The fly is liable to attack the sheep whenever the tem- 

 perature is not too low for its existence, the months of June and 

 July being those in which its depredations are most to be feared. 



Crcatnwnt. 



This is of two kinds, preventive and surgical. A practical 

 method of prevention consists in smearing the noses with a mix- 

 ture composed of tar and grease in equal parts, rubbing it on with 

 a brush. "Where the owner has only a few sheep to take care of 

 this individual dressing of the animals may be feasible, and to 

 be effective should be applied at least once a week throughout 

 the fly season. Where large flocks are kept it becomes an ex- 

 ceedingly difiicult matter to secure them from the attacks of this 

 pest. It is a good plan to herd them during the hot part of the 

 day (when the fly is most active) on dusty ground, the dust 

 raised by the sheep tending to prevent the onslaught of the flies. 



Surgical Crcatmctit. 



This is only resorted to where the removal of the larvae is 

 absolutely necessary, the owner desiring to keep the animal for 

 breeding purposes, and its life being threatened by the attack. 

 It consists in trephining the skull at the frontal sinus, the open- 

 ing being made, according to Turn, as follows: "Cut off the 

 wool which covers the forehead. Trace with colored chalk a 

 transverse line uniting the middle of the two eyebrows and 

 divide it by another line passing at the middle of the forehead. 



