[MACLEODi THE RESPIRATORY CENTRE 93 



exceptional results were obtained in blood removed in about one hour 

 after decerebration, and subsequent experience has taught us that a 

 longer period than this should have been allowed for the ether to have 

 been expelled from the body. Throughout the remainder of the 

 observations the carbonate of the arterial blood remains practically 

 steady. It is impossible to say from the few results on hand and the 

 small degree of fluctuation in the blood-carbonate values whether any 

 parallelism exists between them and those of the aveolar CO2. 



4. Determination of the total acidity and ammonia content of 

 the urine has not supplied results that can be satisfactory interpreted. 

 In practically all cases, of this group as well as of others, in which 

 sufficient urine was obtainable to estimate both the acidity and the 

 ammonia content, a direct proportionality has been observed between 

 the two, so that to follow changes in the acid excretion in a given cat 

 either the titration or the ammonia values may be used. In the three 

 experiments of this group in which there are adequate data a very 

 decided decline in the acid concentration is observed, in fact in two 

 of the animals, XXVI and XXIII, the urine became nearly neutral. 

 Whether this result depends upon a failure of the kidney to remove 

 acid radicles from the blood or upon a relative increase in fixed alkali 

 in the organism cannot be said. 



5. The hydrogen-ion concentration of the arterial blood remained 

 normal, at Pjj 7-4, in one of the animals, but it became less, i.e. Ph 

 became greater (7 -6-7 -7) in two of them (XVIII and XXIII). On 

 account of technical difficulties it was impossible to secure sufficient 

 data to make certain that these changes are real, but further observa- 

 tions will be published shortly. If a real increase in Ph does occur it 

 would indicate that the decreasing acidity of the urine, above referred 

 to, is dependent upon alkali retention. 



6. Lactic acid was determined in the arterial blood of three of the 

 experiments. In two of them (XXVI and XXIII) it varied between 

 0-081 and 0-101 per cent. In the third (XIV) it was much higher, 

 namely, 0-175 per cent. It is important to note that the last estima- 

 tion is possibly too high because the extraction with ether had to be 

 performed in two portions of the unevaporated protein-free filtrate. 

 This would relatively increase the error due to any impurities in the 

 reagents. 



It is of interest in this connection to place on record results ob- 

 tained for lactic acid in the blood of two cats which were bled solely 

 for this purpose immediately after anaesthetising with ether. These 

 are as follows: 0-052 per cent (Cat No. XXVIII) and 0-113 per cent 

 (Cat No. XXIX). It is clear that considerable variation exists in 



