150 



PEACTICAL PHYSIOLOGY 



To correct the volume of gas to and 760 mm. the following formula 

 is employed : 



y V H-/ 



~l+t. 0-00367 ' 760 



where H = the observed pressure, / the tension of aqueous vapour at 

 the observed temperature t. The value of 1 +. 0-00367 and of/ are 

 obtained from tables (cf. Button's Volumetric Analysis}. 



In determining the metabolism of an organ simultaneous samples 

 are taken from an artery and from the vein leaving 

 the organ. The samples can conveniently be col- 

 lected in glass bulbs fitted with short lengths of 

 pressure tubing and clips; the bulbs hold about 

 10 c.c. and are rinsed out with oil. From these 

 the blood is rapidly transferred to the blood- 

 receiver, half-a-dozen of which are exhausted and 

 weighed ready for an experiment. 



The average amount of blood gases obtained is 

 about 60 vols. per cent. Arterial blood contains 

 approximately : 



N 2 , 2 vols. 2 , 20 vols. C0 2 , 40 vols. 

 Venous blood contains approximately : 



N 2 , 2 vols. 



2 , 12 vols. C0 2 , 48 vols. 



FIG. 132. e, Mercury 

 vessel ; t, eudiometer ; 

 p, potash pipette. 



The following is an example of the differences 

 found between the arterial going to, and the 

 venous blood coming from, the thigh muscles of the dog : 



C0 2 

 2 



Rest. 

 + 8-76 

 - 12-92 



Tetanus. 

 + 13-90 

 - 13-75 



As the flow of blood through the muscles in activity is 3-5 times 

 greater, the results obtained during activity must be multiplied by 3 

 to 5. The exact increase in rate of flow can be found by noting the 

 time in which the blood-collecting bulbs fill. The differences in the 

 blood gases in the arterial blood going to, and in the venous blood 

 coming from the brain may be contrasted with the above. They were 

 as follows. An epileptic fit was excited by injection of oil of absinthe. 



C0 2 

 2 



Rest. 



+ 3-87 

 - 3-42 



Activity. 

 + 4-06 

 - 4-95 



Here again the rate of blood flow was increased 3-5 times during the 



fit. 



