1835.] < on Respiration. 31 



out at a natural expiration, is sixteen cubic inches. My 

 nephew, Dr. Andrew Steel, who was a tall man, (about six 

 feet,) with an expanded chest, also made many trials, and 

 satisfied himself that his ordinary expiration was sixteen 

 cubic inches. Messrs. Allen and Pepys determined the 

 volume of air expired by them at an ordinary expiration, to 

 be sixteen and a half cubic inches. From these facts, I 

 think we are entitled to conclude that a common expiration 

 does not much exceed sixteen cubic inches. 



If these data be correct, and they cannot be very far from 

 the truth, it will be very easy to calculate the quantity of 

 carbon thrown out of the body daily by respiration. Allow- 

 ing 20 respirations per minute, and 16 cubic inches of air 

 taken in and thrown out at each respiration, we have 

 28,800 respirations in 24 hours, and 460,800 cubic inches 

 of air passing through the lungs. Of this |I 2 or 17141*76 

 cubic inches are converted into carbonic acid gas. Now 100 

 cubic inches of carbonic acid weigh very nearly 50 grains : so 

 that the weight of carbonic acid formed is 8,570*8 grains, 

 f x ths of which, or 2337*5 grains are carbon. This amounts 

 to nearly nine ounces avoirdupois, or somewhat more than 

 half a pound. 



Article IV. 



On the Changes produced in the Composition of the Blood by 

 repeated Bleedings. By Thomas Andrews, Esq. 



The object of the following experiments is to determine 

 with precision, the changes which are produced in the com- 

 position of the blood by repeated abstractions of large quan- 

 tities of it from the general circulation. In the human 

 subject, opportunities seldom occur of procuring proper 

 specimens for examination, although the operation of vene- 

 section is so frequently performed, as in those cases where 

 it requires to be repeated at short intervals the blood is 

 generally in a morbid state. Instead of waiting for such 

 casual occasions, I directed my attention to those animals 

 in which the composition of the blood is nearly the same as 

 in man, conceiving that similar results would in either case 

 be produced. I selected the blood of calves for the purpose 

 of experiment, and as it is the practice of butchers in this 



