THE CIRCULATION OF THE BLOOD. 



3*5 



diameter it is considerably enlarged on its two sides. The bulbs are 

 fastened to a metallic disk which rotates around an axis in the metallic 

 base which carries the tubes to be inserted into the arteries. With 

 this device it is possible to place either bulb in connection with the 

 proximal end of the artery. Previous to the experiment the proximal 

 bulb is filled with oil, the distal bulb with serum or normal saline. 

 On removing the clips on the artery the blood flows into the proximal 

 bulb and drives the oil into the distal bulb. As soon as the former is 

 filled with blood the bulbs are reversed and the same relative condi- 

 tions are attained. This is repeated a number of times. Knowing 

 the capacity of the bulbs, and the number of times they are filled in 

 a given period, the total quantity of blood discharged is obtained. 

 This divided by the sec- 

 tional area of the artery 

 gives the velocity. The fol- 

 lowing values have thus 

 been obtained: For the 

 carotid of the dog, 205 to 

 357 mm. per second; for 

 the carotid of the horse, 

 306 mm. ; for the metatar- 

 sal artery ,of the horse, 56 

 mm. (Volkmann). For the 

 carotid of rabbits, 94 to 226 

 mm.; for the carotid of 

 the dog, 349 to 733 mm. 

 (Dogiel). 



The variations in the 

 velocity of the blood in the 

 arteries during the different 

 phases of the cardiac cycle 

 have been determined by 

 Chauveau and Lortet with 

 the hemodromograph (Fig. 

 149). This consists of a 



metallic tube carrying a graduated disk. At one point the tube is per- 

 forated but covered with a rubber band through which passes an index. 

 When the tube is inserted into the divided ends of an artery, the cur- 

 rent of blood strikes the short arm of the index and gives to the outer 

 long arm a movement in the opposite direction. The extent of the ex- 

 cursion indicates the velocity. The apparatus is first graduated with 

 currents of water of known velocity. With this instrument Chauveau 

 found that in the horse the velocity during the systole was 520 mm. 

 per second, at the beginning of the diastole 220 mm. per second, and 

 during the pause 150 mm. per second. 



FIG. 149. THE HEMODROMOGRAPH or CHAU- 

 VEAU AND LORTET. A, B. Tube inserted 

 in artery. C. Lateral tube connected with 

 a manometer. b. Index moving in a 

 caoutchouc membrane, a. G. Handle. 



