DISEASES OF THE HEART. 241 



no rare occurrence among horses. The heart has heen known to acquire double 

 its natural volume, or the auricle and ventricle on or.e side have been thus 

 enlarged. Mr. Thomson of Bath relates, in The Veterinarian, a very singular 

 case. A horse was brought with every appearance of acute rheumatism, and 

 was bled and physicked. On the following day he was standing with his fore 

 legs widely extended, the nostrils dilated, the breathing quick and laborious, 

 the eyes sunk in their orbits, the pupils dilated, his nose turned round almost 

 to his elbow, sighing, and his countenance showing approaching dissolution. 



The pulse had a most irregular motion, and the undulation of the jugular 

 veins was extending to the very roots of the cars. He died a few hours 

 afterwards. 



The lungs and pleura were much inflamed ; the pericardium was inflamed 

 and distended by fluid ; the heart was of an enormous size and greatly in- 

 flamed ; both the auricles and ventricles were filled with coagulated blood ; 

 the greater part of the chordae tendineaB had given way ; the valves did not 

 approximate to perform their function, and the heart altogether presented a 

 large disorganized mass, weighing thirty-four pounds. The animal worked 

 constantly on the farm, and had never been put to quick or very laborious 

 work. 



Dilatation is increased capacity of the cavities of the heart, and the parietes 

 being generally thinned. It is probable that this is a more frequent disease than 

 is generally supposed ; and from the circulating power being lessened, or almost 

 suspended, on account of the inability of the cavities to propel their contents, 

 it is accompanied by much and rapid emaciation. In the Gardens of the Zoolo- 

 gical Society of London this is a disease considerably frequent, and almost 

 uniformly fatal. It attacks the smaller animals, and particularly the quadru- 

 mana, and has been found in the deer and the zebra. It is characterised by 

 slow emaciation, and a piteous expression of the countenance ; but the mis- 

 chief is done when these sy mptoms appear. 



Ossification op the Heart. — There are too many instances of this both in 

 the right and the left auricles of the heart, the aortic valves, the abdominal 

 aorta, and also the bronchial and other glands. Mr. Percivall observes of 

 one of these cases, that " the cavity could have been but a passive receptacle for 

 the blood, and the current must have been continued without any or with 

 hardly any fresh impulse." 



Of air in the heart destroying the horse, there are some interesting 

 accounts ; and also of rupture of the heart, and aneurism, or dilatation of the 

 aorta, both thoracic and abdominal, and even farther removed from the heart 

 and in the iliac artery. The symptoms that would certainly indicate the 

 existence of aneurism are yet unknown, except tenderness about the loins and 

 gradual inability to work, are considered as such : but it is interesting to know 

 of the existence of these lesions. Ere long the veterinary surgeon may possibly 

 be able to guess at them, although he will rarely have more power in averting 

 the consequences of aneurism than the human surgeon possesses with regard to 

 his patient. 



This will be the proper place to describe a little more fully the circulation of 

 the blood, and various circumstances connected with that most important 

 process. 



THE ARTERIES. 



The vessels which carry the blood from the heart are called arteries (keeping 

 air,— the ancients thought that they contained air). They are composed 

 of three coats ; the outer or elastic is that by which they are enabled to 

 yield to the gush of blood, and enlarge their dimensions as it is forced along 



R 



