THE CIRCULATORY SYSTEM. 209 



deposits have been erroneously described as fatty degenera- 

 tion. They are generally seen, to a more or less marked 

 degree, in prize beasts, and must be considered normal, for 

 in no case has it been proved that they interfere with the 

 heart's action. 



Os cordis is the name applied to a bony nodule, generally 

 somewhat triangular in form and flattened on each side, 

 which constitutes a basis for attachment of the muscular 

 fibres of the heart, and is situated at the base of the 

 ventricles in connection with the aortic opening. It is an 

 ossification of the fibrous ring of the heart, such as is 

 seen in the horse in exceptional cases. Sometimes this 

 bone consists of two parts, and frequently it involves the 

 whole aortic ring. 



Diseases of the Heart are primarily divided into 

 functional and organic. In the former we have not yet 

 been able to trace the lesions upon which the disorder 

 depends. Such probably exist in the complex cardiac 

 nervous mechanism. Dr. Pettigrew has especially investi- 

 gated this mechanism in the ox (see his ' Physiology of the 

 Circulation in Plants, in the Lower Animals, and in Man '). 

 When we consider that the pneumogastric nerve, pulmonary 

 plexus, and the medulla oblongata, certainly are sources of 

 nervous supply to the heart, we shall be inclined to 

 attribute '^ functional " disease of the heart to our present 

 want of knowledge of structural changes in the case 

 rather than to absence of disorder of so complex a me- 

 chanism. 



Palpitation is the form which this nervous disorder 

 generally assumes, but it is rare in the ox, this animal not 

 as a rule being subjected to extremes of exertion, nor to 

 high strains upon the nervous system. Dyspepsia causes 

 this disorder probably by reflex inhibition through the 

 vagus, while in blood poisoning the impurities in the blood 

 probably do so by acting directly upon the cardiac ganglia 

 and the muscular fibres of the heart ; perhaps, too, there is 

 perverted stimulation of the inner surface of the heart, as 

 in anaemic palpitation, when venous murmurs are marked 

 and the impoverished blood tends to clot around the 



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