THE DIAPHRAGM. 233 



liary in the act of parturition. In its quiescent state, it presents its convex surface 

 towards the thorax, and its concave one towards the abdomen. The anterior 

 convexity abuts upon the lungs ; the posterior concavity is occupied by some 

 of the abdominal viscera. The effect of the action of this muscle, or the con- 

 traction of its fibres, is to lessen the convexity towards the chest, and the 

 concavity towards the abdomen : or perhaps, by a powerful contraction, to 

 cause it to present a plane surface either way. The abdominal viscera that 

 must be displaced in order to effect this, have considerable bulk and weight ; 

 and when the stomach is distended with food, and the motion required from 

 the diaphragm in rapid breathing is both quick and extensive, there needs 

 some strong, firm, elastic, substance to bear it. The forcible contact and 

 violent pressure would bruise and otherwise injure a mere muscular expan- 

 sion ; and therefore we have this tendinous expansion, comparatively devoid of 

 sensibility, to stand the pressure and the shock which will always be greatest 

 at the centre. 



Yet it is subject to injury and disease of a serious and varied character. 

 Whatever may be the original seat of thoracic or abdominal ailment, the 

 diaphragm soon becomes irritable and inflamed. This accounts for the breathing 

 of the horse being so much affected under every inflammation or excitement of 

 the chest or belly. The irritability of this muscle is often evinced by a singular 

 spasmodic action of a portion, or the whole of it. 



Mr. Castley thus describes a case of it : " A horse had been very much dis- 

 tressed in a run of nearly thirteen miles, without a check, and his rider stopped 

 on the road towards home, to rest him a little. With difficulty he was brought 

 to the stable. Mr. Castley was sent for, and he says, ' When I first saw the 

 animal, his breathing and attitude indicated the greatest distress. The promi- 

 nent symptom, however, was a convulsive motion, or jerking of the whole 

 body, audible at several yards' distance, and evidently proceeding from his 

 inside ; the beats appeared to be about forty in a minute. On placing my hand 

 over the heart, the action of that organ could be felt, but very indistinctly ; 

 the beating evidently came from behind ^he heart, and was most plainly to be 

 felt in the direction of the diaphragm. Again placing my hand on the abdo- 

 minal muscles, the jerks appeared to come from before backwards ; the 

 impression on my mind, therefore, was, that this was a spasmodic affection of 

 the diaphragm, brought on by violent distress in running*.' " 



Mr. Castley's account is inserted thus at length, because it was the first 

 of the kind on record, with the exception of an opinion of Mr. Apperley, 

 which came very near to the truth. " When a horse is very much exhausted 

 after a long run with hounds, a noise will sometimes be heard to pro- 

 ceed from his inside^ which is often erroneously supposed to be the beating 

 of his heart, whereas it proceeds from the excessive motion of the abdominal 

 musclest." 



Mr. Castley shall pursue his case, (it will be a most useful guide to the 

 treatment of these cases) : " Finding that there was little pulsation to be felt 

 at the submaxillary artery, and judging from that circumstance that any 

 attempt to bleed at that time would be worse than useless, I ordered stimu- 

 lants to be given. We first administered three ounces of spirit of nitrous ether, 

 iu a bottle of warm water ; but this producing no good effect, we shortly after- 

 wards gave two drachms of the sub-carbonate of ammonia in a ball, allowing 

 the patient, at the same time, plenty of white water to drink. About a quarter 

 of an hour after this, he broke out into a profuse perspiration, which continued 

 two hours, or more. The breathing became more tranquil, but the convulsive 



* The Veterinarian, 1831, p. 247. t Nimrod on the Condition of Hunters, p. 185. 



