658 TRANSACTIONS OF SECTION I. 
at least, an increase in the excretion of both creatinin and creatin. The following 
table shows this :— 
Effects of Methyl Citrate. 
Preformed Creatinin. Total Creatinin. 
Observation, 
Feeding. Injection. Feeding. Injection. 
Per cent. Per cent. Per cent. Per cent. 
3a Nil Nil Nil Nil 
4a 11°5 Die? 2°2 16°5 
5a 3°6 3°4 l-l 18 
The general conclusion is that while the greater part of the arginin adminis- 
tered by injection is transformed into urea, some of it appears to be converted 
into creatin in the dog, and part of this latter to be excreted in the. urine as 
creatinin and creatin. The amount thus excreted was considerably increased (in 
one observation) by a simultaneous injection of methyl citrate. Feeding with 
methyl citrate in this experiment reduced the output of creatinin and creatin. 
In two other cases feeding with the citrate had no influence. 
The proportion of arginin nitrogen which reappeared as creatin was, in 
observation 1, 7 per cent. ; in observation 2, 6°5 per cent. ; in observation 3, 6 per 
cent.; in observation 4, 16 per cent. The effects here given for arginin and 
methyl citrate are obtained by deducting the effects of methyl citrate alone, in 
each experiment, from the total effects of the combined substances. 
8. The Action of the Corpus Luteum on Metabolism. By W. Sack. 
9. Pulmonary Gaseous Exchange in Apnea. By T. H. Mitroy, M.D. 
The apnoea which is produced in animals by forced pulmonary ventilation with 
air is evidently independent of the degree and rate of distension of the lungs so 
long as the total amount of air driven through the lungs remains the same. 
After freezing the vagi, apnoea can be produced in the same way as with the 
vagi intact. This period of apna can be markedly altered by replacing the air 
in the lungs at the close of the pumping by various gas mixtures. In all cases 
where gas mixtures rich in oxygen are employed in this way, the duration of 
apnoea is markedly lengthened ; in fact, the increase so produced is as great as if 
the ventilation throughout had been carried out with the mixture. On the other 
hand, gas mixtures which contain amounts of carbonic acid greater than that 
present in ordinary air produce shortening of the period of apnoea. As the 
carbonic acid in the gas mixture is raised, a point is at last reached when there 
is at first a loss in the carbonic acid present in the alveolar air, this point 
evidently indicating that percentage of carbonic acid which corresponds to a 
partial pressure of that gas above that present in the alveolar air at the begin- 
ning of apneea. With gas mixtures which contain 10 per cent. or more carbonic 
acid breathing starts very shortly after cessation of ventilation. When the air 
in the lungs after prolonged ventilation is replaced by nitrogen there pass out 
into the alveolar air both oxygen and carbonic acid. The oxygen which passes 
out under those conditions does not rise above four per cent., nor the carbonic 
acid above a slightly lower limit. In all cases where oxygen or air is left in 
the alveoli at the outset of apnoea, the consumption of oxygen takes place more 
rapidly than the excretion of carbonic acid, the respiratory quotient in the case 
where air is used being from 0°3 to 0°4. The passage out of carbonic acid from 
blood to alveolar gas mixtures seems to be mainly if not entirely dependent upon 
the difference of the pressure of that gas in blood and alveoli, and not upon the 
nature of the gas mixture in the alveoli. Thus carbonic acid passes out prac- 
tically at the same rate from blood in lungs to alveolar gas mixtures, be those 
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