334 On the Quantity of Carlonic Acid Gas [Nov. 



and termination of the minimum, the words " the ending," and 

 " beginning of twilight," should be adopted. 



Sjsct. II. — Experiments made to ascertain the effects of some 

 substances upon the quantity of' carbonic acid emitted from the 

 lungs during respiration, 



I am happy to find some of the results of my former experiments 

 corroborated in a considerable degree by another. Dr. A. Fyfe, jun. 

 of Edinburgh, last summer turned his attention to this subject, and 

 unknown to me made some experiments very similar to my own, 

 and likewise extended his researches to other objects. This 1 was 

 informed of by his brother some time afterwards; and in conse- 

 quence of my expressing a wish to him of knowing the results, Dr. 

 F. was so obliging as to communicate them to me generally in a 

 letter, dated Nov. 4, 1813 ; when I had the gratification of learning 

 that, as far as we had proceeded together, we had arrived at similar 

 conclusions. This gentleman's experiments are now published,* 

 and hence I shall not scruple to mention some of their particulars. 



Dr. F. fixed the standard quantity of carbonic acid gas emitted 

 from his lungs under ordinary circumstances of health, &c. at about 

 S-5 per cent.f Having ascertained this by repeated experiments, 

 he tried the effects of the following subjects : — 



1. Vegetable Diet. — This reduced the quantity of carbonic acid 

 to about 4*5 per cent. 



2. Animal Diet. — The effects of this were various, and consider- 

 ably different. 



3. Wine. — This reduced the quantity, in one experiment, to 

 between two and three per cent. ; in another, to 5*75 per cent. 



4. Mercury. — When the body was completely under the effects 

 of this metal, the quantity was reduced to about three per cent. 



5. Nitric Acid. — A course of this reduced the quantity to be- 

 tween six and seven per cent. 



1. Vegetable Diet. — A course of this was commenced on the 

 11th of May, and continued for eight days ; on the fifth day of the 

 experiment there was no difference in the quantity of carbonic acid ; 

 on the seventh and eighth day the quantity was reduced as above 

 stated. 



2. Animal Diet. — A course of this was begun on the 31st of 

 May, and continued for the same time as the above ; on the fourth 

 day the quantity of carbonic acid was seven per cent. ; on the 

 seventh and eighth clays, five per cent. This experiment was re- 



* See Dissertatio Chemico-Physiologica Inaugurate de Copia Acidi Carbonici e 

 Pulmonibiis inrer respirandum evoluti. Auctore Andrea Fyfe, jun. Ediuburgi, 

 W.DCCC.X1V.- 



t TV apparatus employed by Dr. F. consisted of a vessel open at bottom, and 

 furnished with a proper valve, which contained about 150 cubic inches. This was 

 filled with water, ;n)d inverted in a pneumatic trough, and the air from the lung* 

 repeatedly inspired ihroii^h lie valve till it was full. The proportions of carbonic 

 acid and oxygen were then ascertained by means of Hope's eudiometer, and the 

 assistance of lime-water and sulphuret of lime. 



