186 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



comes off passes into the tube c, which was originally filled up to the 

 zero mark with water in continuity with that in the reservoir A. This 

 would depress the column of fluid in c and raise that in the open 

 tube D, which is graduated in millimetres. In practice, however, it 

 is convenient to keep the gas always at the same volume : this may 

 be done by raising the pressure in the open tube (D) by squeezing 

 some of the water with which the gauge is filled out of a rubber 

 reservoir B, which forms the base of the gauge ; thus the level of the 

 water in c is kept at the zero, while that in D rises from H to i. 

 The actual measurement then is the increase of pressure (i.e. the 

 height of the column of water HI) which is necessary to keep the 

 gases in the tube c at the same volume as that which was previously 

 occupied by the air in that tube. From this the quantity coming off 

 can be calculated. 



The chemical method is not quite so accurate as the vacuum pump, 

 but it is much more convenient for the study of many problems, as it 

 requires less blood, and, owing to its simplicity, a great number of 

 observations can be made upon a single animal. 



Changes in Tissue Respiration caused by Activity. In all organs, 

 so far as is known, increased activity is associated with increased 

 tissue respiration. The increase is commonly three- to six-fold. It is 



Organ 



Muscle . 



Heart , 



Submaxillary 

 gland 



Pancreas 



Oxygen 



Condition of rest j used per ! Condition of activity 

 minute 



Nerves cut < 0-003 c.c. | Tonic (nerves 



uncut) 



Oxygen used 

 per minute 



0-006 c.c. 

 0-020 c.c. 



Very slow and 0-007 c.c. Normal contrac- 0*014 

 feeble contrac- ; tions 



tions Very active i 0*054 



Nerves cut 0-04 c.c. Chorda tympani 0-12 c.c. 



stimulated 



Not secreting 0-05 c.c. Secretion after in- 

 jection of secre- 

 tin 



0-20 



