viii BLOOD- STKEAM: MOVEMENT IN VESSELS 259 



On the other hand, the method still occasionally adopted after 



Fio. 100. Hiirthle's recording haemodromometer, partly schematic, partly in section, a, b, Can- 

 nulae connecting with central and peripheral ends of artery ; c, well-calibrated glass cylinder 

 into which the blood flows, pushing the piston now from above downward, now from below 

 upwards. The piston is connected by a thread passing over two pulleys, to the lever d, 

 which records on a rotating drum the movements of the piston, i.e. the filling or emptying of 

 the cylinder. Below the metal plate which supports the measuring cylinder is a movable 

 disc e, with handle, /, connected with the metal band g, which turns the disc 180, reversing 

 the current and crossing the rubber tubes a' V. Before applying the apparatus, the whole of 

 the tubing a, a', b, b', c is filled with physiological saline. This is effected by the tube h carry- 

 ing a tap, which is shut off when the tubes are completely filled. 



Harvey (who first employed it to measure the velocity of the 

 circulation) is entirely fallacious, since it is based on the amount 



