162 SCIENCE PROGRESS 



observations, found that with both these organisms the C0 2 dis- 

 charge showed an immediate and progressive diminution from 

 the moment the nitrogen was substituted for air. For instance, 

 three snails kept in air at 19/6 gave out C0 2 at the rate of 

 322 c.c. per kilogram per hour. In nitrogen the rate of discharge 

 dropped in successive half-hours to 202, 136, and 104 c.c, and 

 then for the remaining five hours of the experiment to 80-90 c.c. 

 Altogether 644 c.c. of C0 2 were given out in six and a half hours, 

 whilst in another experiment at the same temperature no less 

 than 1,088 c.c. were given out in the same time. These animals, 

 therefore, contained a very much larger amount of separable 

 C0 2 in their tissues than frogs do, for even at the end of these 

 two experiments the C0 2 was still coming off at a fairly rapid 

 rate. The caterpillars experimented with did not show quite so 

 remarkable a result as this, but in six and a half hours at 17*5° 

 they gave out C0 2 amounting to 446 c.c. per kilogram, and 

 during a further twenty-two hours they gave out 532 c.c. more, 

 or 978 c.c. in all. 



In the case of warm-blooded animals it is obvious that 

 exposure to an atmosphere of nitrogen would cause death and 

 cessation of C0 2 discharge in a very few minutes. A liberation 

 of C0 2 by the tissues does not absolutely cease, however, for 

 the writer found that if an excised mammalian kidney be perfused 

 with oxygenless saline it continues to give off C0 2 for some 

 hours. This C0 2 rapidly dwindles down, and after an hour or 

 two falls to 15-14 c.c. per hour per kilogram, but it was found 

 that altogether nearly 100 c.c. per kilogram was discharged. 

 The amount varied but little, whether the temperature of per- 

 fusion were 15 , 20 , or 28 , just as Aubert found it to vary 

 but little in the frog. Whether mammalian tissues as a whole 

 contain much less separable C0 2 than amphibian tissues it 

 is impossible to say, for it is probable that the C0 2 stored 

 up in the different organs of an animal varies considerably, 

 being, for instance, large in muscle and small in nerve. But 

 at least we may conclude that it is very much larger in 

 the snail than in the caterpillar, and in the caterpillar than in 

 the frog. 



And by what processes is this C0 2 formed in the tissues in 

 the absence of oxygen ? Engelmann, Pfluger, and others sup- 

 pose that the protoplasm of the cells, when exposed to oxygen, 

 has the power of binding it and storing it up in an intramolecular 



