THE CIRCULATION. 



315 



tion quickens the flow in the jugular, expiration lessens it. During 

 each auricular cycle the blood-flow in the jugular ceases, when the 

 period of rising pressure ensues. He also found in the femoral vein 

 that variations in the venous flow accompanying a tetanic muscular 

 contraction may be divided into three periods: (1) period of great 

 flow synchronous with the muscular shortening ; ( 2 ) period of slight 





Fig. 105. Tachogram (V), Sphygmogram (P) , from the Carotid of 

 Horse made with Chauveau's Haemodromograph and a Sphygmograph at 

 the same time. (LORTET.) 



The abscissa, o, o, corresponds to the zero-line of rapidity. The dicrotic 

 wave is marked on the curve. The slightly curved ordinates drawn through 

 the curves indicate corresponding points on the two curves. The vertical line, 

 1, indicates the moment the ventricular contraction sends the first systolic wave 

 into the carotid, which calls out simultaneously an increase of blood-pressure 

 and of rapidity of the current of blood. The vertical line, 2, is the time the 

 pressure of the blood has reached its height, whilst the rapidity is decreasing. 

 The vertical line, 3, corresponds to the period when the ventricle has been 

 emptied of blood, and closing of the semi-lunar valves ensued. The vertical 

 line, 4, is the moment of the rebound of the column of blood from the semi- 

 lunar valves and the dicrotic pulse is produced. Between 3 and 4 the rapidity 

 falls below the zero-line and shows a rebound of the rapidity of the blood when 

 the rapid dicrotic rise ensues. From 4 to 1, the curve of arterial tension is 

 slowly falling, and at the same time the rapidity decreases much more slowly. 



flow continuing during the contracted state of the muscle; (3) short 

 iriod of increased flow following the relaxation of the muscle. 



Rate in the Capillaries. Even with respect to the capillaries 

 the rule holds good that the velocity is inversely proportional to the 

 uva of cross-section. In the frog and in man the velocity has been 

 stimated to be about one-inch per minute. 



