THE SENSORIAL FUNCTION. 73 



1 The thyroid, helmet -shaped, cartilage, inclosing and shielding the neighbouring parts. 



2 The epiglottis, or covering of the glottis, or aperture of the wind-pipe. 



3 The arytenoid, /M7i7»eZ-«Aoped, cartilages, having between tliem the aperture leading into 



the trachea or wind-pipe. 



4 One of the chordae vocales, cords or ligaments concerned in the formation of the voice. 



5 The sacculus laryngis, sac or ventricle of the larynx, or throat, to modulate the voice. 



6 The trachea, or wind-pipe, with its ditTerent rings. 



7 The soft palate at the back of the mouth, so constructed as almost to prevent the possibiUty 



of vomiting. 



8 The opening from the back part of the mouth into the nostril. 



9 The cartilage covering the entrance into the eustachian tube, or communication between 



the mouth and internal part of the ear. 



10 The oGSophagus, or gullet. 



11 The cricoid, ring-like, cartilage, below and behind the thyroid. 



12 Muscle of the neck, covered by the membrane of the back part of the moutli. 



The sinus on the different sides of the forehead do not communicate with each 

 other, but with other sinuses in the ethmoid, and spenoid, and upper jaw-bones, and 

 also with the cavities of the nose on their respective sides. These sinuses afford a 

 somewhat increased protection to the brain beneath; and by the continuous and 

 slightly projecting- line which they form, they give beauty to the forehead ; but their 

 principal use probably is, like the windings of the French born, to increase the clear- 

 ness and loudness of the neighing. It will be remarked that they are very irregular 

 in depth, which at one place is an inch or more. 



In the sheep, and occasionally in the ox — rarely in the horse — the larvae of maggots 

 produced by certain species of flies, crawl up the nose, lodge themselves in these 

 sinuses, and produce intolerable pain. 



Veterinary surgeons have availed themselves of these sinuses, to detect the exist- 

 ence of glanders, that disease so infectious and so fatal. They may suspect that a 

 horse respecting which they are consulted is glandered. It is of great consequence to 

 be sure about this. The safety of the whole team may depend upon it. It may be 

 a puzzling case. There may be no ulceration of the nose within sight. The glands 

 under the jaw may not be close to and seemingly sticking to the bone, which is a 

 common symptom, yet for a considerable time there may have been a discharge from 

 the nostril, and the horse is out of condition. On the other hand, some slight ulcera- 

 •i m may be detected in the nostril, but the horse eats well, works well, and is in 

 good plight. It is possible that from the closest examination of the animal, no horse- 

 man or veterinary surgeon can give a decided opinion. 



If, however, tne horse is glandered, there will probably be considerable ulceration 

 in the upper part of the cavity of the nose, and a collection of matter there. To 

 ascertaiu this the veterinary surgeon sometimes makes an opening into these sinuses. 

 He may do it with perfect safety. On that part of the frontal bone, which lies between 

 the eye and the pit above it, and above the inner corner of the eye, there is, on either 

 side, a small depression or hole (see fig. b, cut, page 70), which may be easily felt in 

 the living horse. It is what anatomists call a foramen — the supra-orbital foramen. It 

 gives passage to the blood-vessels and nerves of the forehead. 



Supposing a line to he drawn across the forehead, from one of these depressions to 

 the other on that line, and about half an inch from the centre of it — it matters not on 

 which side — the frontal sinuses will be found an inch in depth (compare fig. 6, pp. 

 70 and 72. There a perforation may be easily and safely made. A little way above, 

 the brain would be endangered, and a little below this line, the cavity of the nose 

 would be pierced. Some warm water may be injected into this hole, with a common 

 squirt, and it will run out at the nose. If there is matter in the frontal sinuses, or 

 any part of the cavity of the nose, below the indirect opening from the sinus into the 

 nose under the superior turbinat.'d tone, it will appear mixed with the water, and the 

 owner may be assured that the horse is glandered ; but if tlie water flows uncoloured, 

 or simply mixed with blood ot mucus, the horse rnay be considered as free from this 

 disease. The thick creamy c jnsis^ence of pus, its sinking in water, and its capability 

 of being perfectly, although not readily, mixed with water, will distinguish it sufti- 

 cientlj' from tne natural discharge from the nose, which is ropy, lighter than water, 

 and, when mixed witn it, f nil preserves a kind of stringiness. 

 7 K 



