PHYSIOLOGICAL EFFECTS OF CARBONlC ACID^ ETC. 91 



would take place in accordance with the following equa- 

 tion : — 



Indigo-blue. Alcohol. Formic acid. 



2(C,eHi3NO«)+ioHO = 2(C,eH,NO,) + 3(C,H3 0,)+4(C,H,0,). 



It will be seen that the same law regarding the number 

 of atoms of oxygen prevails here as in the case of the bodies 

 before described^ this number being either 8 or lo. 



If in this process ordinary alcohol is replaced by methylic 

 alcohol, the same effect is produced, provided acetate of 

 soda is employed; but a mixture of methylic alcohol, 

 formiate of soda, and caustic soda does not act in the same 

 manner on indigo-blue, which remains unchanged, however 

 long it may be left in contact with the boiling liquid. It 

 appears, therefore, that one of the two agents, ethylic alcohol 

 or acetic acid, is quite essential. One of the two may be 

 replaced by an homologous body ; but when both are so 

 replaced, the indigo-blue remains intact. 



IV. On some Physiological Effects of Carbonic Acid and 

 Ventilation. By R. Angus Smith, Ph.D., F.H.S., F.C.S., 

 President of the Society.. 



Read January 24th, 1865. 



In a report on the air of mines and confined places, there 

 was given a chapter on the action of the pulse when car- 

 bonic acid accumulated in the air. It is proposed to repeat 

 that chapter, and to supplement it with additional experi- 

 ments. The experiments, when not otherwise explained, 

 were made in an air-tight lead chamber described in the 

 report alluded to. It may be well first to show the amount 

 of carbonic acid exhaled. This will be done by giving the 



