90 PRACTICE OF MEDICINE. 



the suppuration of which should be kept up for a long time, or by a 

 moxa. As all febrile symptoms subside, we may improve tl)e 

 patient's diet by allowing light broths, fresh eggs, ^c. ; diuretics 

 should also be now had recourse to. In this stage, Dr. Stokes 

 places great reliance on the internal and external use of iodine. 

 When the absorption of the effused fluid has been effected, change 

 of air should be recommended. 



Paracentesis. — If effusion into the pleura is so extensive as to en- 

 danger the patient's life from the difficulty of breathing it occasions ; 

 or if his health and strength are giving way, it will be proper to 

 make an aperture for the escape of the liquid hy paracentesis, 



DISEASES OF THE HEART AND ITS MEMBRANES. 



Auscultation of the heart in health. — On applying the ear to the 

 region of the heart in a healthy person, a sound is heard at each 

 pulsation, followed by an interval of silence. This sound is double, 

 consisting of a dull slow sound, immediately followed by a short 

 quick one. The first sound is produced by the contraction (systole) 

 of the ventricles, and is synchronous with the pulse of arteries near 

 the heart. The second, or short one, accompanies the dilatation 

 (diastole) of the ventricles. This second sound is said to be pro- 

 duced by the shock caused by the tightening of the semilunar valves 

 at the ventricular diastole. Laennec rates the relative duration of 

 these sounds to be as follows — The first sound, two-fourths ; the 

 second sound, one-fourth, or a little more ; the interval of silence, 

 one-fourth, or a little less. These sounds are naturally most dis- 

 tinct in the space between the cartilages of the fourth and seventh 

 ribs of the left side, and on the lower part of the sternum ; the for- 

 mer part corresponding with the left, and the latter with the right 

 side of the heart. Simultaneously with the first, or systolic sound, 

 an impulse or shock is communicated to the stethoscope. It is most 

 jptible at and between the cartilages of the fifth and sixth ribs, 

 ^re it may be felt by the hand ; but the stethoscope commonly 

 renders it sensible in lean persons over the whole praecordia. Con- 

 siderable variety in the force of the impulse may occur from various 

 extraneous causes acting on a healthy heart. Thus, the pressure of 

 tumours behind it, flatulent distension of the stomach, great enlarge- 

 ment of the liver and spleen, contraction of the chest from pleurisy, 

 deformity of the spine, and similar causes, which have the effect of 

 pushing the heart into closer contact with the anterior walls of the 

 chest, will make its impulse against them stronger. Again, exten- 

 sive effusions of air or liquid in the left pleura may displace the 

 heart, so that its impulse can only be felt under or even to the right 

 of the sternum. The action of the heart is naturally accelerated by 

 exercise, stimulating drinks, heat, &c. ; and this excited action is 

 attended with an increased impulse and with louder sounds. 



