222 PRACTICE OF EQUINE MEDICINE. 



What are the forms ? 



There are two forms recognized, one being dilatation with 

 thickening, and the other dilatation with thinning. 



Give the aetiology. 



Weakening in the walls of the cavities, together with increased 

 pressure, are the main factors in producing dilatation. 



Changes in the heart muscle, adhesions of the pericardial sac, 

 increased amount of blood in the heart, excessive work, valvular 

 disease, and lung diseases are among the causes of dilatation. 



What is the morbid anatomy? 



Dilatation is more frequently present in the right side of the 

 heart and is usually associated with hypertrophy of one or more 

 of the cavities. Great distention causes an incompetency of the 

 valves, thus allowing regurgitation. 



The endocardium may be opaque, especially in the auricles, 

 and marked alterations are shown by the use of the microscope. 



Give the symptoms and physical signs. 



A dropsical condition may be the result in some cases, the 

 pulse becomes weak and rapid, the breathing difficult, and signs of 

 obstructed venous circulation are present. 



On percussion, the area of dulness is increased, a condition 

 very difficult to determine in the horse. 



On auscultation, the first sound is shorter and sharper, some- 

 what resembling the second sound. 



Give the indications for treatment. 



In some cases stimulants, as ammonia or alcohol; digitalis is 

 especially indicated in dilatation; strophanthus may be used as a 

 substitute for digitalis. Other drugs indicated are iron, arsenic, 

 strychnine, morphine. Purges in some cases. Avoid over-exertion 

 and give concentrated food. 



CAEDIAC PALPITATION. 



Give the synonyms. 



Palpitation of the heart; irritable heart. 



