142 



PRACTICAL PHYSIOLOGY 



gases. On the lower end of F is a three-way tap. To the upper 

 end of F is fixed a piece of thick small-bored pressure tubing pro- 

 vided with a clip. 



The mercury used to 

 fill the pump must be 

 cleaned and the pump 

 evacuated before use. In 

 using the pump the 

 manipulations are as fol- 

 low : F is placed in the 

 position indicated by the 

 dotted line. A is raised 

 and B is put in connec- 

 tion with F, and F is 

 filled with mercury. The 

 clip on the rubber tube 

 at the upper end of F 

 is then closed, and A 

 lowered until F is ex- 

 hausted, except for 2 or 

 3 c.c. of mercury which 

 are purposely left within. 

 The screw-clip on the 

 lower end of F is next 

 closed, and F is then 

 detached from the pump 

 and weighed. A sample 

 of blood is, with due pre- 

 cautions, now withdrawn 

 by opening the clip into 

 connection with F. It is 

 now detached, and the 

 blood is defibrinated by 

 shaking it with the mer- 

 cury left within F for the 

 purpose. F is then again weighed, and the weight of the sample 

 obtained. F is next affixed to the tube E, and E is exhausted. 

 Finally the screw clip 

 between E and F is 

 opened, and the gases 

 are withdrawn and col- 

 lected in the eudio- 

 meter. To facilitate 

 the escape of the gases 

 F is placed in warm 

 water and shaken. If 

 the blood froths too 

 violently the frothing 

 can be allayed by pouring some warm water on the tube E, 



FIG. 136. Leonard Hill's blood-gas pump. 



FIG. 137. The three-way tap of the mercury 

 pump. 



The. 



