144 



EXPERIMENTAL PHYSIOLOGY 



to produce a gradual increase of force of the auricle, and a less marked 

 change in the ventricular contraction when 5 c.c. of a - l per cent, 

 solution are injected. Neurine is found to cause a slight slowing of 

 the beat and a rapid decrease in force of the auricle, soon followed by 

 a gradual increase to about double its initial contraction, and then the 

 effect slowly disappears. Upon the ventricle the changes are in the 

 same direction, though very much less in amount. 



To complete the demonstration the animal may be killed by 

 asphyxia. For about the first half-minute the auricular beats increase 

 in amount, remain at this height for some time, and then slowly begin 

 to decrease. The ventricle beats remain practically the same for 

 about H minute, and then a very rapid change sets in. Some of the 

 ventricle beats are dropped and the auricle beats faster ; both decrease 

 greatly in force, and there is at first an increase in general tone, which 

 is rapidly replaced by a decrease in tone, and then the beats gradually 

 decrease and the animal dies. As soon as the rapid change in the 

 heart begins, the right auricle is seen to become more and more filled 

 with blood and soon becomes greatly distended ; a condition which 

 persists up to death. 



For the purpose of the examination of the heart in man we 

 possess an instrument whose working should be studied in the follow- 

 ing experiment : — 



Experiment I. — Take a tracing of your own heart's impulse by means of 

 the cardiograph (fig. 114). This consists of a tambour, f, the lower end of 



Fig. 114. — The Cardiograph. 



which is closed by a rubber membrane, g, on the centre of which is cemented 

 a thin aluminium' disc, h. The cavity of this tambour is placed in communica- 

 tion with a second, the recording tambour, fig. 34, by the tube b. The tambour 

 is fixed on three arms, and at the ends of these are three legs, a 1 , a 2 , and a\ 

 which can be screwed up or down and thus allow a vertical adjustment of 



