CONTENTS 
Exact physiological regulation of the blood-gases. 
Evidence that CO, acts physiologically as an acid. 
Investigations of the reaction of blood. 
Extreme delicacy of the physiological regulation of 
the blood reaction. 
Regulation of the blood-reaction by the lungs, liver, 
and kidneys. 
Effects of want of oxygen on the breathing. 
High balloon ascents, CO poisoning, and mountain 
sickness. 
Acclimatisation to oxygen want :—the Anglo-Ameri- 
can Expedition to Pike’s Peak in 1911. 
Acclimatisation effects of oxygen want on the 
breathing. 
Acclimatisation effects on the haemoglobin percent- 
age and blood-volume. 
Acclimatisation effects on active secretion inwards of 
oxygen by the lungs. 
Factors in acclimatisation to want of oxygen. 
III. REGULATION OF THE ENVIRONMENT, INTER- 
NAL AND EXTERNAL 
Further analysis of oxygen secretion by the lungs. 
Secretion of oxygen by the swim-bladder. 
Secretion in other glands. 
Analogy between secretion and cell-nutrition. 
The circulatory regulation of carriage of oxygen 
and CO,. 
Regulation by vaso-motor nervous control. 
Evidence that this control depends upon the metabo- 
lism of the tissues. 
Evidence that the heart’s action in pumping blood 
depends on the same conditions. 
Part played by contraction of the veins. 
The blood as a constant internal environment. 
Regulation of this internal environment by the kid- 
neys. 
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