DISEASES OF THE CIRCULATORY SYSTEM. 73 



CHAPTER IV.— DISEASES OF THE CIRCU- 

 LATORY SYSTEM. 



Introduction. — There is a simplicity about the circula- 

 tory apparatus of the dog which renders it but little liable 

 to disease ; indeed, the works on Canine Pathology of two 

 well-known authors have no notice of this important system 

 of organs. Doubtless with increasing knowledge of the 

 subject we shall gradually learn that cardiac diseases of an 

 organic form are most frequent in sporting dogs ; those of a 

 functional nature in toy breeds. The heart is thin walled 

 and almost globular in form ; the apex is directed back- 

 wards, and the right side lies against the upper surface of 

 the sternum ; but, as the breast bone is inclined obliquely 

 downwards and backwards, the difference in the position 

 of the heart between carnivora and herbivora is not great. 

 The apex is rounded and formed by both ventricles, and 

 the two sides are fairly equal in size. The pericardium 

 is posteriorly attached to the tendinous portion of the 

 diaphragm. The arterial and venous systems are capacious 

 and well developed, but the lymphatic apparatus is small 

 in proportion, although the receptaculum chyli is large 

 and runs far forwards in the chest. The relative develop- 

 ment of blood and lymph systems as above explained is 

 quite in accordance with the sanguine temperament of 

 the animal. It is estimated that the heart of the dog 

 may vary from '3 to '7 per cent, of the weight of the animal. 



Fibrous deposits on the valves of the heart result 

 from rheumatism. They form a rough surface on which 

 fibrin becomes deposited before death, and the clot may 

 prove fatal by occluding the cardiac openings or entangle- 

 ment of the valves in such a way as to interfere with their 



