INFLUENCE OF THE FREQUENCY OF THE RESPIRATIONS. 339 



taking the mean of the times of 100 clocks instead of employing 

 one costly but reliable chronometer,) Vierordt's experiments appear 

 to us fully to merit the confidence which their author himself places 

 in them. One of the most essential requirements towards the 

 success of such experiments undoubtedly consists in the power of 

 carrying on the normal respirations in a quick and undisturbed 

 manner, and in this respect Vierordt has a decided advantage over 

 Stiirmer. The latter observer obtained the following mean quan- 

 tities from eight or ten experiments with the expired air. 



C Respiratory movements in the minute yielded 5'45 percent, of carbonic acid. 

 12 4-57 



24 3-50 



48 2-65 



According to Vierordt's experiments, 500 cubic centimetres [or 

 30*5 cubic inches] are about the mean value for the volume of the 

 air expelled by one expiration when the breathing is undisturbed. 

 If now we assume, during hurried respiration, an equally large 

 volume for the air expelled by each expiration, the absolute amount 

 of carbonic acid exhaled in a minute may be very readily calculated 

 from the above data. The following table plainly shows the rela- 

 tions deduced from this calculation. 



Vierordt subjoins some interesting remarks on the number of 

 respirations which must be made in a minute in order to remove 

 the whole of the carbonic acid from the blood circulating through 

 the lungs. If, for instance, we assume with him that the quantity 

 of carbonic acid in the blood passing in one minute through the 

 pulmonary capillaries amounts to 4300 c. c. [or 262 cubic inches], 

 it would require, according to the above data, upwards of 

 300 respiratory acts for its entire removal ; for 192 respirations 

 would only remove 2496 c. c. [or 152 cubic inches], whilst 

 twice that number might separate as much as 4896 c. c. [or 

 299 cubic inches,] supposing that such excessive frequency of 



Z2 



