RESPIRATION IN A CLOSED SPACE. 267 



As the total amount of C0 2 and found in the entire blood, at any 

 one time, is only 4 grammes, and as the daily excretion of C0 2 = 900 

 grammes, and the absorbed daily = 744 grammes, it is clear that 

 exchange of gases must go on with great rapidity, that the absorbed 

 must be used quickly, and the C0 2 must be excreted. 



Still, it is a striking fact that oxidation-processes of such magnitude as, e.g., 

 the union of C to form C0 2 , occur at a relatively low temperature of the blood 

 and the tissues. It has been assumed that the blood acts as an ozone-producer, 

 and transfers this active form, of O to the tissues. Liebig showed that the 

 alkaline reaction of most of the juices and tissues favours the processes of oxida- 

 tion. Numerous organic substances, which are not altered by O alone, become 

 rapidly oxidised in the presence of free alkalies, e.g., gallic acid, pyrogallic acid, 

 and sugar; while many organic acids, which are unaffected by ozone alone, are 

 changed into carbonates, when in the form of alkaline salts (Gortip-Besanez), and in 

 the same way, when they are introduced into the body in the form of acids, they 

 are partly or wholly excreted in the urine, but when they are administered as 

 alkaline compounds they are changed into carbonates. 



133. Respiration in a Closed Space, 



Respiration in a closed or confined space causes : (1) a gradual 

 diminution of O ; (2) a simultaneous increase of C(X> ; (3) a diminu- 

 tion in the volume of the gases. If the space be of moderate dimensions, 

 the animal uses up almost all the contained therein (Nysten), and 

 dies ultimately from spasms caused by the asphyxia. The is absorbed, 

 therefore independently of the laws of absorption by chemical means. 

 The in the blood is almost completely used up (Setschenow). In a 

 larger closed space, the C0 2 accumulates rapidly, before the diminution of 

 O is such as to affect the life of the animal. As C0 2 can only be ex- 

 creted from the blood when the tension of the C0 2 in the blood is greater 

 than the tension of C0 2 in the air, as soon as the C0 2 in the surrounding 

 air in the closed space becomes the same as in the blood, the C0 2 will 

 be retained in the blood, and finally C0 2 may pass back into the body. 

 This occurs in a large closed space, when the amount of is still 

 sufficient to support life, so that death occurs under these circumstances 

 (in rabbits) through poisoning with C0 2 , causing diminished excitability, 

 loss of consciousness, and lowering of temperature, but no spasms 

 (Worm Miiller). In pure 0, animals breathe in a normal way; the quantity 

 of absorbed and the C0 2 excreted is quite independent of the percentage 

 of 0, so that the former occurs through chemical agency independent of 

 pressure. In closed spaces filled with 0, animals died by re-absorption 

 of the C0 2 excreted. Worm Miiller found that rabbits died after absorb- 

 ing C0 2 equal to half the volume of their body, although the air still 

 contained 50 per cent. 0. Animals can breathe quite quietly a mixture 

 of air containing 14'8 per cent. (20'9 per cent, normal); with 7 per cent. 



