152 A MANUAL OF VETERINARY PHYSIOLOGY 



Apoplexy of the Lungs arises as the result of overwork, especially 

 in hot weather ; but it may also occur in the winter. Horses ridden 

 to death in the hunting field, in the name of ' sport,' die as a rule 

 from pulmonary apoplexy ; the lungs cannot get rid of their abnormal 

 burden of blood to the left heart. 



Bronchitis is probably rarely a disease distinct from pneumonia. 

 1 Broken Wind ' is one of the most interesting of the various chest 

 diseases of the horse ; it is a condition peculiar to this animal, liable 

 to occur suddenly, and frequently traced to errors in dieting. To 

 state the case shortly, the lungs lose their power of elastic recoil, and 

 do not collapse even after death ; the respirations are greatly in- 

 creased, the expiratory effort being powerful, characteristically 

 irregular, and prolonged. A chronic typical cough becomes estab- 

 lished, and the animal unfit for anything but slow work. On post- 

 mortem examination the lungs are found to fill the chest entirely ; 

 they cannot collapse, for all elastic recoil has left them. One 

 of the fundamental errors in veterinary pathology is to attribute 

 this condition to emphysema or asthma. 



Roaring is a nervous affection, to which sufficient allusion is made 

 in the section dealing with the larynx. One point may be established 

 in consequence of the frequency with which the larynx is now 

 surgically dealt with, and that is, an injury to a cartilage of the 

 larynx is always followed by thickening and ossification, with con- 

 sequent reduction in the lumen of the larynx. 



Spasm of the Diaphragm is another respiratory affection due to 

 disordered nervous supply. The sound emitted is quite unlike that 

 in the human ; it appears to come from within the chest or abdomen, 

 and is represented by a dull ' thud ' like a magnified heart-beat, 

 which, in its frequency and regularity, it closely resembles, and for 

 which it may easily be mistaken. 



Rupture of the Diaphragm is a common lesion frequently due to 

 disorders of the digestive canal, the gas generated in the intestine 

 being sufficient to burst the diaphragm. Falls are by no means an 

 uncommon cause ; for example, an animal falls on to its head, and 

 the abdominal viscera are propelled against the diaphragm. The 

 diaphragm rarely gives way below, almost always above, and in the 

 tendinous substance rather than the muscular. This point is of 

 physiological interest. 



Catarrh. — As the horse can only breathe through the nostrils ; 

 obstruction of these passages from catarrh render the animal unfit 

 for work, even when no other symptoms of importance are present. 

 In the facial sinuses collections of pus are frequent and troublesome. 



Laryngitis is frequently the result of strangles infection, rarely 

 of ordinary cold. In the former condition local oedema and dyspnoea 

 are not infrequent, and arise suddenly. 



In the ox pneumonia is rare, with the exception of the specially 

 highly infectious type, constituting one of the animal plagues. 

 Practically none of the other diseases mentioned above as affecting 

 the horse are found in any ruminant. 



The number and character of the respirations is not only a trust- 

 worthy guide during the onset and progress of disease, but their 

 character may be absolutely diagnostic. Broken wind and hydro- 

 thorax may be determined by a glance at the flanks ; stertorous 

 breathing suggests cerebral compression ; while any noise accom- 

 panying the inspiratory act in the horse is suggestive of commencing 

 oedema of the pharynx or larynx. 



