342 



OF THE CIRCULATION OF THE BLOOD. 



found that great diminution in the rapidity of the flow of blood followed 

 section of the spinal cord, which was clearly due to the consequent paralysis 

 of the vaso-motor nerves, and the accumulation of blood in the veins of the 

 viscera. The instrument adopted by M. Lortet 1 (Fig. 148) is founded on 

 the same principle as the one suggested by MM. Chauveau, Bertolus, and 

 Laroyenne. 2 It consists of a short tube, open at both ends (a), which is 

 introduced into the artery. On one side, near the middle, is a square open- 

 ing (6), which is closed by a plate or ring of caoutchouc. The caoutchouc 

 is pierced by a long and light lever (c), the short and somewhat broader end 

 of which hangs in the current of blood, whilst the long end records its cor- 

 responding but opposite movements on a rotating drum, the fulcrum being 

 the point where the lever is gripped by the sides of the opening in the india- 

 rubber. Connected with the instrument is a sphygmoscope and a sphygmo- 

 graphic apparatus, with the object of obtaining traces of the pulsations, the 

 tube of the former being soldered on the one hand into the side of the pri- 

 mary or hsemodromographic tube, and on the other being connected with an 

 elastic cushion filled with air, and supporting a lever the movements of which 

 are registered just below those of the lever indicating the rapidity of the 

 movement of the blood. Fig. 149 shows a double normal tracing obtained 

 from the carotid of a horse with a pulse of 40 per minute. Each complete 

 trace, therefore, occupied a second and a half. From this it will be seen 

 that the increase of the rapidity commences briskly, the line of ascent being 



FIG. 149. 



Tracing obtained by M. Lortet's Instrument. 



The scale above indicates tenths of a second. V, tracing indicating the variations in the rapidity of 



the blood. P, tracing of the pulse. 



sharp, and reaching its acme in the space of two-tenths of a second. In the 

 following tenth the line rapidly falls. In the fourth and fifth tenths the 

 rapidity diminishes insensibly, and in the sixth the line is almost horizontal, 

 though still above the zero line. At the seventh tenth second is a slight ele- 

 vation, showing a dicrotism of rapidity. During the succeeding eight-tenths 

 of a second the line, though descending, presents undulations corresponding 

 to oscillations of the rapidity. Amongst the more important results of his 

 observations, M. Lortet believes he has shown that the blood attains its max- 

 imum of rapidity shortly before the systole of the heart, as indicated by the 



1 Kccliorclics snr la Vitesse du Cours du Sung, etc., Paris, 18U8. 



2 Journal de la Physiologic, IJrown-Scquard, 18GO, t. iii. 



