Larva of CEstrus Ovis in Ihe Nasal Sinuses of Sheep. 115 



directed toward the centre of the mass and held low so that the 

 fly cannot reach them. The moment the fly touches the nose they 

 shake the head, stamp with the feet, and gallop off with the nose 

 close to the ground, looking from side to side to see if the fly pur- 

 sues and frequently smelling at the grass as if apprehensive of 

 other flies hidden there. If such appear they instantly turn and 

 scamper to other parts of the field or take refuge in a dry dusty 

 place or gravel bank. 



The young larva when deposited on the nostril speedily makes 

 its way up and takes refuge in the cavities of the turbinated bones 

 and the frontal and maxillary sinuses, where it passes the winter 

 feeding on the mucus and the purulent discharges determined by 

 its presence. When mature it leaves the nose and assumes the 

 chrysalis form in the soil. 



The mature larva is narrow anteriorly, broad behind : its 

 upper surface is prominent and rounded, lower surface flat, and 

 furnished at the anterior of each ring after the third, with a series of 

 pointed tubercles or spines : the cephalic end bears the buccal or- 

 gans directed downward, and bearing two great hooks connected 

 with the hard framework of the pharynx and recurved downward, 

 backward and outward ; mouth small ; antennse thick and short 

 placed above the buccal organs : the inferior part of the last ring 

 projects beyond the upper portion and is furnished with two 

 nodules with intervening spines : pentagonal patches of stigmata 

 on the last ring : very small anterior stigmata between the first 

 and second rings. The color is white with brown spines, stig- 

 mata and transverse strise. Ivcngth seven lines to one inch. 



When dropped from the nostril in the course of summer they 

 pass into chrysalis in one or two days ; and after a residence of six 

 or eight weeks in the soil emerge as the perfect fly. 



Morbid Symptoms Caused by the Larvae in the Head. 

 Grub in the Head. These bear a close relation to the number 

 of larvae present. If there are only two or three no trouble may 

 result. If many there is muco-purulent discharge from the nose, 

 snifiling breathing, frequent sneezing and snorting expelling mu- 

 cus and even blood ; shaking of the head ; rubbing of the nose 

 on the fore legs or other objects ; weeping eyes ; and occasional 

 unsteadiness of the gait. 



In the worst cases the respiration becomes sighing, wheezing or 



