The acquisition of oxygen by the blood in the lung 195 



analysis. Yet there are many limitations to this principle, especially 

 on the biological side. Many are the fortunes which have been lost 

 in commerce because the reaction which will take place in the test 

 tube will not take place in the works. The reasons are in many cases 

 apparent. I have been told that in a brewery of great repute the 

 chemical staff found it impossible to reproduce in the laboratory the 

 reactions which took place in the vat because the vat unlike the 

 beaker is practically an adiabatic system, its ratio of cooling surface 

 to volume as compared with that of the beaker is relatively infinites- 

 imal its substantial walls are poor conductors of heat. With the 

 advent of an adiabatic beaker in the shape of a Dewar's vessel, the 

 conditions of the vat can be reproduced, and with the conditions 

 the reactions. 



In the case of physiological requirements the younger generation 

 has grasped the principle that everything depends upon working 

 with the minimal possible quantity of gas. 



This is so from whatever view you take it. Biological conditions 

 change so rapidly that the technique of the biologist must be one 

 which can be operated with great rapidity. Moreover they become 

 changed and abnormal by the mere abstraction of the quantities of 

 fluid required for the older methods. In the viscid fluids of the body 

 the process of abstraction of the gases is a much more difficult one 

 than it is in the case of the limpid liquids with which the chemist 

 deals, and is greatly facilitated by increasing the ratio of surface to 

 volume ; i.e. in general by decreasing the volume used. Then again 

 gas analysis is a very special sort of analysis inasmuch as the 

 measure of the gas is usually its volume, and this is extremely 

 sensitive to temperature and pressure. How great would be the 

 anxiety of the analytical chemist to reduce the amount of matter 

 which he weighed to the smallest possible bulk, if before he weighed 

 it he had to convince himself that it was of uniform temperature 

 throughout and that its temperature was known to a hundredth of a 

 degree. Nor have I stated the case as urgently as I might. I have 

 said that the measure of a gas is its volume. In practice this is not 

 the case, the measure of the gas is usually a measurement of length, 

 it is the distance between two points on a cylindrical burette. If 

 there is a temperature error, that will be three times as apparent as 

 it would be if the gas were free to expand or contract along all three 

 of its linear dimensions. It has therefore been the object of the 

 younger school of physiological gas analysts to cut down the quantity 



132 



