READJUSTMENTS OF REGULATION 35 
might well retort by asking what regulates all the 
complex conditions concerned in the process—the for- 
mation and marshalling of haemoglobin and salts in 
the corpuscles, and the astoundingly delicate balance of 
the various substances which are concerned in the 
carriage of CO,. 
Nevertheless the regulation of both the breathing 
and the carriage of gas by the blood can be disturbed, 
either temporarily or for long periods; and it is only 
by studying these disturbances that we can get further 
insight into the regulation. It has already been men- 
tioned that when mineral acids are administered the 
breathing increases, so that the alveolar CO, pressure 
necessarily falls, while the amount of CO, in the 
arterial blood may be diminished in acid poisoning 
to a small fraction of what it normally is. The 
administration of alkalies has a similar effect in the 
opposite direction. Slighter effects of a similar kind 
can be brought about, at least temporarily, by mere 
changes in diet. In diabetes a condition sometimes 
occurs in which a great excess of organic acid is 
formed in the body; and this also is accompanied by 
great increase in the breathing and fall in the alveolar 
CO, percentage. A temporary effect in the same 
direction follows exposure to want of oxygen, or 
excessive muscular exertion. It was known that expo- 
sure to great want of oxygen leads to the production 
of lactic acid in the body, and that excessive muscular 
exertion must have the same effect, since the amount 
of work done excludes the possibility of the circula- 
tion being able to supply the muscles with the oxygen 
