MOVEMENT OP THE BLOOD IN THE ARTERIES. 



489 



throughout, as at B, all communication with the glass tube is cut off : on the 

 other hand, when the communication with the glass tube is opened, as at C, 

 the channel of the horizontal tube is stopped, and fluid entering at a', would 

 have to pass through Ji', and to traverse both limbs of the glass tube (p, p) 

 emerging at a. For the protection of the instrument in using it, the glass 

 tube is attached to a board, to which is fixed a scale marked in metal. 



In order to use the instrument, a large artery is freely exposed for not 

 less than three inches, and, after due precaution has been taken to counteract 

 hemorrhage, it is divided by cutting out a piece ; the conical pipes (&, k') 

 are then fixed into the open ends of the artery, one being directed towards the 



heart, the other towards the capillaries. -They must be fixed far enough apart, 

 to admit of the introduction of the horizontal tube (A) between them, without 

 altering the usual direction of the arterial stream. When this tube is fitted to 

 the conical pipes, then the bent glass tube, previously filled with water, must 

 be fixed to it by means of the short tubes Qi, h r , C), the stopcock being so 



