370 Messrs. G. A. Buckmaster and J. A. Gardner. [Aug. 19, 



would not vary directly as the change in ventilation. From these considera- 

 tions we might expect the oxygen content of arterial blood to fall a little 

 below the normal and the carbon dioxide to augment, and to a slight extent 

 also the nitrogen, at about the point of the vanishing of the reflexes in the 

 initial stages of anaesthesia, and in the second stage of anaesthesia. On the 

 other hand, when the animal is recovering from the anaesthetic and the lung 

 ventilation is improving, we might expect the gas-content of the blood at 

 the reappearance of the reflexes to again approach the normal, or even be 

 normal. In Table XV we give analyses, taken from our paper on " The 

 Composition of the Blood Gases in Chloroform Narcosis,"* and the blood gases 

 at the various stages referred to. 



Table XV.— Gas Content of the Arterial Blood of Cats at 0° and 760 in c.c. 

 per 100 c.c. of Blood. 







co 2 . 



O. 



N. 



1 



Normal (average of six observa- 



tions) 



25 -07 



13 -60 



1-0 



2 



Disappearance of reflexes (in 

 3—5 mins.) 



27 -76 

 26-45 

 34 51 



9-52 



6- 11 



7- 71 



3-05* 

 2-03* 

 1 -38 



3 



Ee-appearance of reflexes after 

 cessation of CHC1 3 for 

 25—35 mins. 



26 -62 

 26 -31 

 32 -83 



15-41 

 12 -14 

 12 -58 



1 -18 

 1-19 



1 -28 



4 



Second stage of anaesthesia (aver- 

 age of eight experiments) 



36 -00 



8-14 



1 -49 







16 98—48 -38 



3 -51—11 -63 



1 -16—2 -53 







* Uncorrected for the nitrogen contained in the oxygen used for combustion of the 

 chloroform. 



In normal cats the amount of haemoglobin, as given by the Gowers-Haldane 

 hajmoglobinometer, lies between 70 and 80, which, in terms of the percentage 

 of oxygen content, would give a value a little above 13-6, the average volume 

 of oxygen found by gas analysis. The fall in oxygen content during the 

 second stage of anaesthesia is about 40 per cent., and in the initial stages 

 often even more than this. The haemoglobin is then only partially saturated 

 with oxygen during narcosis — indeed not more than 60 per cent. The 

 blood of the normal cat, on the assumption that the alveolar air contains 

 14 per cent, of oxygen, must, when allowance is made for tension of aqueous 

 vapour at 38° (49-3 mm.) and with 40 mm. carbon dioxide tension in blood, 

 * ' Journ. Physiol.,' Nov. 9, 1910, vol. 41, p. 255. 



