CAI^CIFICATION OF THE HEART. 



Calcification of the cardiac walls and especially of the auricles, 

 has been met with a number of times in the horse and ox, yet 

 strangely enough, there is no record of it in the dog, though that 

 animal is often allowed to live out his days, and is, moreover, 

 specially exposed to heart-strain and heart disease. That small 

 animals are not exempt is shown in the remarkable case in a wild 

 duck quoted under dilatation. 



Causes. It has been attributed to old age, glanders, endocar- 

 ditis and pericarditis, to which may be added dilatation. The 

 primary change is usually the formation of fibrous tissue by the 

 organization of an exudate. The continuous strain on this 

 organizing exudate in connection with dilatation, appears to be 

 a stimulus to the calcareous deposit, which is especially common 

 in the thin, yielding walls in the right heart. The affected 

 auricle may be several times its natural capacity and the terminal 

 ends of the veins may show a saccular distension, yet it is rare to 

 find a calcification of the venous walls. To this the thin, yielding 

 walls of the asygos sometimes make an exception. 



Lesions. The calcified centres are sometimes in isolated plates, 

 from a millimeter to several centimeters in diameter, and other 

 times the whole roof and walls of the right auricle are involved. 

 Even with extensive calcification the different plates often remain 

 united by intermediate fibrous material, so that the normal con- 

 tractions of the heart can still, in some measure, continue. The 

 plates are red, hard, resistant, and crackle under the knife 

 about as does the cancellated tissue of bone. Toward the margins 

 they are paler and devoid of lime salts resembling the foetal car- 

 tilage of ossifying bone. Under the microscope are found 

 the large, round cartilage cells, merging into the stellate osteo- 

 blasts, but scattered irregularly through interweaving bundles of 

 white, fibrous tissue in place of being arranged in Haversian 

 systems. 



Symptoms. In some cases no symptoms, even of heart disease, 

 have been observed ; horses have gone about ordinary, moderate 

 work without manifest inconvenience, just as the fat wild duck, 

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