348 



RESPIRATION. 



vation in reference to this subject, which may, I think, prove of 

 some interest towards the further elucidation of this question. I 

 have found that frogs lose much less of their weight in a dry than 

 in a moist atmosphere, the difference being very considerable. 

 The two following of my numerous observations may suffice to 

 demonstrate this difference. In one case 100 grammes' weight of 

 frogs lost 1*820 grammes of their weight in twenty-four hours in a 

 dry atmosphere, and as much as 4*376 grammes during the same 

 period of time in moist air; in another experiment they lost 0'68 1 

 of a gramme in dry, and 5*340 grammes in moist air. It is very 

 obvious that these conditions depend chiefly upon the perspiration, 

 and do not, therefore, present a perfectly parallel case with the 

 respiration of the higher animals ; for the external appearance of 

 the frogs which were in the dry air, showed that their skin was dry, 

 and consequently in an unfit state for carrying on the process of 

 respiration ; but still this observation may not be entirely uncon- 

 nected with these respiratory conditions. It also shows the 

 necessity for practising caution in drawing our conclusions from 

 experiments made on animals which have only respired a perfectly 

 dry air. We cannot possibly observe normal conditions of respi- 

 ration in experiments conducted merely in dry air, although this 

 one element may not be of great importance in reference to the 

 consideration of the whole process. 



The pressure of the air is another of the atmospheric influences 

 which reacts upon the respiration. We will here first refer to the 

 most recent experiments made in relation to this subject, partly 

 because they are limited to respiration in the human organism, 

 and partly because they have led to the adoption of far more correct 

 views regarding the influence of atmospheric pressure than could 

 be obtained from the earlier observations on animals. Here too 

 we are mainly indebted to Yierordt for our knowledge. His 

 numerous experiments at different heights of the barometer yield 

 the following values for the individual functions of respiration. 



