RESPIRATION BEYOND THE LUNGS 



381 



the walls of the vessel, perfect equilibrium between the atmosphere and 

 the fluid may be attained (see page 338). A measured quantity of hemo- 

 globin solution (0.1 or 1.0 c.c.) is then removed from each tonometer 



Fig. 134. Barcroft's tonometer for determining the curve of absorption of oxygen by hemoglobin 

 or blood. (From Starling's Physiology.) 



and placed, together with some very dilute ammonia to lake the blood, 

 in one of the small bottles of the differential manometer, shown in Fig. 

 135.* This manometer consists in principle of a graduated U-shaped 

 tube of narrow bore, containing clove oil, the free end of the U-tube 



Fig. 135. Barcroft's differential blood gas manometer. The capillary U-tube contains clove oil. 

 The pockets on the sides of the blood bottles should be deeper. For manipulation see context. 



being connected with small bottles provided with some device so that 

 two fluids can be placed in each of them but kept unmixed until the 

 bottle is violently shaken. The three-way stopcock between the small 



*The blood-gas manometers are made in two sizes for use with 1 c.c. and 0.1 c.c. quantities of 

 blood, respectively. The results with these small quantities are as accurate as with larger amounts. 



