In carrying out this task the place selected should be as quiet ■ as possible, and the attention of the examiner should be fixed upon the sounds given out during respiration. The position he takes up should be to windward, so that the sound emitted may be conveyed towards him. Wherever the examination is being conducted he should take up a position alone, and not allow his attention to be diverted from its purpose by any conversation with others. Noisy dogs in dealers' yards, the shouting of men, and cracking of whips are not calculated to render this part of the examination as satisfactory as it should be.
In drawing a conclusion upon this test regard must be paid to the fact that the breathing sounds emitted by different horses are liable to some variation within the limits of health, according among other things to condition, formation of the face, setting on of the head, temperament, etc. Space will not allow us to examine these several questions here. Suffice it to say that any noise which partakes of the nature of roaring or whistling is an indication of unsoundness, and denotes the existence of some obstructive disease in the respiratory passage leading to the lungs. In a very large majority of cases the defect is located in the larynx, the entrance to which becomes narrowed in consequence of paralysis of the small muscles, whose duty it is to keep the passage open.
Thickening of the mucous membrane of the larynx from cold, influenza, and strangles, enlargement of neighbouring glands, and tumours about the throat may each and all, by their pressure and narrowing influence, be the means of causing roaring.
Tumours and bony excrescences in the nostrils may also give rise to the nasal form of this unsoundness.
" Punching" is a test commonly resorted to by dealers, and consists in striking the animal suddenly over the body with a stick or the closed fist, followed up with a succession of feints to repeat it while the animal is firmly held against a wall. The test is not a reliable one, although in the majority of roarers it causes the emission of a deep, sonorous grunt. It is, however, useful in the sale-yard, where no opportunity is afforded of resorting to other means.