330 NASAL CAVITIES. 



their appetite, but become thinner, and the condition shows no tendency 

 to spontaneous cure. 



Treatment. The only rational treatment consists in trephining, an 

 operation practised immediately above the maxillary tuberosity and over 

 the lowest part of the sinus (Fig. 164). This opening allows the cavity 

 to be washed out and the sinus drained. 



Antiseptic treatment exactly resembles that of purulent collections 

 in the frontal sinus. Injections of astringents, dilute carbolic acid and 

 iodine solutions, etc., are recommended. 



OESTRUS LARV^ IN THE FACIAL SINUSES OF SHEEP. 



(false sturdy.) 



Causation. This disease of sheep, which sometimes produces vertigo 

 resembling that shown in gid or sturdy, is produced by the growth of 

 larvae of CEstrus ovis in the frontal sinuses. The oestrus of the sheep 

 assumes perfect insect form during the fine days of summer from July to 

 September. The females swarm around the flocks and attempt to alight 

 on the animal's head close to the nostrils, where they deposit their eggs 

 or larvae. The larvae crawl into the nostrils, thence into the nasal cavities, 

 the meatus, and finally the sinuses, where they become fixed. In these 

 sinuses they undergo complete development, increasing from a length of 

 about Yo inch to from f to 1 inch before their transformation into the 

 nymph and perfect insect. They remain in the sinus for eight to ten 

 months. When numerous and well developed they may fill the whole 

 of the cavity. 



Symptoms. It is easy for a careful observer to note the time at 

 which the larvae penetrate the sinus. During the hottest hours of the 

 day the adult insects are continually hovering over the flocks, and on 

 watching carefully one sees sheep suddenly become excited, tap with their 

 feet, rub their faces against any hard, resisting object in the neighbour- 

 hood, plunge their nostrils into the dust, and snort violently. 



When the larvae have penetrated the nasal cavities they produce 

 frequent attacks of sneezing by irritating the mucous membrane, and 

 cause an intense sero-mucous and afterwards a moderate muco-purulent 

 coryza. As long as the larvae remain of small size, the apparent results 

 they produce are insignificant, as during the first months of winter ; but 

 when they are numerous, and have become of considerable size, they 

 cause symptoms which might suggest an attack of gid or sturdy. 



Thus the bodily movements become spasmodic, the gait irregular, 

 and the animals show attacks of vertigo. They stagger and fall, making 

 convulsing movements, grinding their teeth and rolling their eyes, while 

 frothy saliva escapes from the mouth, etc. 



