EXTERNAL STRUCTURE. 69 



spinal marrow. Tlie columnar appearance of this portion of the brain is repre- 

 sented; and the origins of the respiratory nerves. 



q The spinal marrow extending through a canal in the centre of the bones of the neck, 

 back, and loins, to the extremities of the tail, and from which the nerves of feehng 

 and of motion, that supply every part of the frame, except the head, arise. 



r The septmn narium, or cartilaginous division between the nostrils. 



A- The same cut off at the lower part, to shew the spongy turbinated, iurban-shaped, bones, 

 filling the cavity of the nostril. 



t The palate. 



u Tlie molar teeth, or grinders. 



V -The inferior maxillary bone, containing the incisor teeth or nippers. The canine 

 tooth, or tush, is concealed by the tongue. 



w The posterior maxillary, or lower jaw with its incisors. 



X Tlie lips. 



y Tlae tongue. 



z A portion of the os hyoides, or bone of the tongue, like a Greek u, v. 



1 Tlie thyroid, helmet-shaped, cartilage, enclosing and shielding the neighbouring parts. 



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



3 Tlie arytenoid, funnel-shaped, cartilages, having between them 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, throat, to modulate the voice. 



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



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



sibility of vomiting. 



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



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



the mouth and internal part of the ear. 



10 Tlie oesophagus, or gullet. 



1 1 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 mouth. 



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

 maggots prodnced by certain species of flies, crawl up the nose, lodge them- 

 selves in these sinuses, and produce intolerable pain. 



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

 existence of glanders, that disease so infectious and so fatal. They may sus- 

 pect that a horse respecting m hich they are consulted is glandered. It is of 

 great consequence to be sure about it. The safety of the whole team may 

 depend upon this. It may be a puzzling case. There maybe 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 ulceration 

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

 good plight. From the closest examination of the animal, no horseman, 

 and no veterinary surgeon can give a decided opinion. 



If, however, the horse be gland ered, there will probably be considerable 

 ulceration in the upper part of the cavity of the nose, and a collection of 

 matter there. To detect this the veterinary surgeon sometimes makes an 

 opening into these sinuses. He may do this 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 depres- 

 sion or hole (see fig. h b, cut, page 66)^ which may be easily felt in the living 



