INFLUENCE OF ATMOSPHERIC PRESSURE. 349 



A rise in the barometer of 5*67'" therefore increases the pulsa- 

 tions 1*3, the respirations about 0*74, and the amount of expired 

 air 586 c. c. [or 35 '7 cubic inches] in a minute, whilst the car- 

 bonic acid of the latter sinks about 0'309. Vierordt further 

 remarks that these differences are made more apparent when respi- 

 ration is carried on at higher temperatures. 



Legallois placed dogs, cats, rabbits, and guinea-pigs in an 

 atmosphere which was only one-third as dense as the ordinary 

 atmosphere, and compared the results of these experiments 

 with others obtained from observations conducted at the ordinary 

 pressure of the atmospheric air. We cannot, however, attach any 

 great value to these experiments, because the sudden change in the 

 atmospheric pressure must necessarily have disturbed the other 

 functions of these animals to so great a degree as essentially to 

 vitiate the purity of the observation. Although my own experi- 

 ments on rabbits and green-finches, in connection with this point, 

 are not free from all grounds of objection, I have endeavoured, as 

 far as possible, to distinguish between the effects of the alternation 

 in the pressure of the air, and those depending upon the constant 

 atmospheric pressure. I found by direct observation, that every 

 rapid change in the pressure of the air, whether this change 

 were one of increase or diminution, gave rise to accelerated respi- 

 ration both in birds and in mammals, and, consequently, that it 

 was connected with increased exhalation of carbonic acid. My 

 experiments were, therefore, conducted in such a manner as to 

 accustom the animals to an increase or diminution of the ordinary 

 atmospheric pressure, after which the quantity of carbonic acid 

 expired within a definite time under such an increased or dimin- 

 ished atmospheric pressure, was determined. The results obtained 

 presented nearly the same degree of variability, although in some 

 cases the pressure was raised to 34", and in others it fell to 22". 

 Although, for instance, in one case 1000 grammes* weight of green- 

 finches exhaled 5 '921 grammes of carbonic acid when the baro- 

 meter stood at 739 m. m., and 6'313 grammes when the barometer 

 was at 805 m. m. the temperature in both cases being + 13, and 

 in another case 1000 grammes' weight of rabbits exhaled 0*529 of 

 a gramme of carbonic acid with the barometer at 704 m. m., and 

 O'GOO grammes with the barometer at 801 m. m., the temperature 

 in both cases being 15, and there would, therefore, seem to be 

 some ground for the hypothesis that an augmentation of the car- 

 bonic acid was due to increased atmospheric pressure ; yet the 

 most general result to be deduced from the tolerably accordant 



