DISEASES OF THE HEART. 



441 



sheep, the goat, and large-sized dogs; from 80 to 120 in small ani- 

 mals. It is lessened in some cerebral affections (subacute encepha- 

 litis, immobility, affections of the cervical bulb and vagus nerve 

 centres) ; it increases in fever, painful diseases, heart diseases, 

 anemia, and hemorrhages. In a normal state, under the influence 

 of exercise, excitement, etc., the cardiac bruit becomes fuller and 

 stronger (this phenomenon is observed in most horses and dogs 

 upon a first examination); it is violent in palpitations, valvular 

 alterations, hypertrophy, in recent endocarditis and pericarditis, ia 

 hepatization or pulmonary indurations located upon the anterior 

 part of the lobes, and during the course of serious febrile condi- 

 tions ; in these latter, its intensity comes in contrast with the weak- 

 ness of the pulse ; the violent bruit is here the expression of the 

 distress of the myocardium. Lessening of the force of the cardiac 

 impulse is due to atony of the heart (insufficient innervation, weak- 

 ening by very elevated temperatures, fatty degeneration and inflam- 

 matory alterations of the cardiac muscle), also to its remoteness 

 from the pectoral walls, due to a pleuritic or pericarditic exudate, 

 by hydrothorax or hydro-pericardium, pneumothorax, or pneumo- 

 pericardium (rare), pulmonary emphysema, to adhesions with the 

 thickened pericardium, etc. In the horse, the precordial impulse 

 is perceptible upon the right side in dextro-cardia, in right cardiac 

 hypertrophy, in febrile diseases (frequent); often, also, when the 

 chest is narrow, it is felt slightly upon the right side. In peri- 

 carditis and endocarditis we observe, beside the cardiac impulse, 

 friction or vibrating noises ; these are related to valvular alter- 

 ations. 



lY. The heart sounds, perceived normally by auscultation and 

 so called in contrast to all heart bruits which are pathological, 

 must be distinguished as first and second; the first is low, long, 

 systolic (it corresponds with the ventricular systole) ; the second is 

 short, clear, diastolic (it corresponds with the beginning of diastole). 

 The interval between the first and the second sound is short (little 

 pause), between the second and the first 'it is long (great pause). 

 The two sounds are Only positively recognized by this single char- 

 acter. The first is produced by the tension and vibration of the 

 auriculo- ventricular valves ; it is perhaps increased by the muscu- 

 lar bruit of the myocardium when it is contracting, by the blood 

 circulation under a strong pressure in the ventricles, and by the 

 concussion of the pectoral walls under cardiac impulsion ; the 



