286 



PRACTICAL PHYSIOLOGY. 



[lx. 



2. Illuminated Ox-Heart (Gad). 



This must be arranged previously by the demonstrator. Two 

 brass tubes with glass windows are tied, one into the left auricle {d) 

 (7 cm. diameter) and the other {<:) into the aorta (5 cm. diameter). 

 These are connected with a large reservoir (R), as shown in the 

 figure. The interior of the heart is illuminated by a small elec- 

 tric lamp if) pushed in through the apex of the heart, and served 



by several small Grove cells. 

 Into the apex is tied a brass 

 tube, which is connected with 

 a large india-rubber bag with 

 thick walls (P). Fill the whole 

 with water. On compressing 

 the elastic bag, fluid is driven 

 onwards, when the play of 

 the valves can be beautifully 

 studied. On relaxation, the 

 mitral valves open and the 

 aortic valves close. 



After each demonstration, 

 remove the glass windows of 

 the cannulse and the caout- 

 chouc tubes, and preserve 

 the heart in 10 p.c. chloral 

 hydrate. 



Fig. 207.— Scheme of Gad's Apparatus to show 

 the play of the Valves of the Heart. A. L. 

 auricle ; d. Its window, and communicating 

 with b, the inlet tube for water from the 

 reservoir, R; V. L. ventricle, illuminated by 

 an electric lamp, I, and communicating with 

 the elastic bag, P ; e. Glass window fixed in 

 tube in aorta ; a. Tube carrying fluid to the 

 reservoir. 



3. The Stethoscope — 

 Heart Sounds. 



{a.) Place the patient or 

 fellow-student in a quiet 

 room, and let him stand 

 erect and expose his chest. 

 Feel for the cardiac impulse, 

 apply the small end of the 

 stethoscope over this spot, and apply the ear to the opposite end of 

 the instrument. The left hand may be placed over the carotid or 

 radial artery to feel the pulse in either of those arteries ; compare 

 the time-relations of the pulse with what is heard over the cardiac 

 impulse. 



{h.) Two sounds are heard — the first or systolic coincides with 

 the impulse, and is followed by the second or diastolic. After this 

 there is a pause, and the cycle again repeats itself. The first sound 

 is longer and deeper than the second, which is of shorter duration 

 and sharper, 



(c.) Place the stethoscope over different parts of the praecordia, 



