226 A MANUAL OF PHYSIOLOGY 



starving organism lives on its own fat and proteids, and 

 has only a trifling carbo-hydrate stock to draw upon. In a 

 diabetic patient, fed on a diet of fat and proteid alone, the 

 respiratory quotient was only "6 to '7, just as in a starving 

 man. 



In an average man weighing 70 kilos the mean produc- 

 tion of carbon dioxide is about 800 grammes (400 litres) in 

 twenty-four hours, and the mean consumption of oxygen about 

 700 grammes (490 litres) (Pettenkofer and Voit). But there 

 are very great variations depending upon the state of the 

 body as regards rest or muscular activity, and on other 

 circumstances. In hard work the production of carbon 

 dioxide was found to rise to nearly 1,300 grammes, and in rest 

 to sink to less than 700 grammes, the consumption of 

 oxygen in the same circumstances increasing to nearly 1,100 

 grammes and diminishing to 600 grammes. In rest, in 

 moderate exertion, and in hard work, the production of 

 carbon dioxide was found to be nearly proportionate to the 

 numbers 2, 3 and 6, respectively. In a case of diabetes the 

 consumption of oxygen was 50 per cent, greater than in a 

 healthy man, corresponding to the higher heat-equivalent 

 of the food of the diabetic patient (Weintraud and Laves). 



Taking 400 litres per twenty-four hours, or 17 litres per hour, as 

 the mean production of carbon dioxide by an average male adult at 

 rest or doing only light work, we can calculate the quantity of fresh 

 air which must be supplied to a room in order to keep it properly 

 ventilated. 



It has been found that when the carbon dioxide given off in 

 respiration amounts to no more than 2 parts in 10,000 in the air of 

 an ordinary room, the air remains sweet. When the carbon dioxide 

 given off reaches 4 parts in 10,000, the room feels distinctly, and at 

 6 in 10,000 disagreeably, close, while at 9 parts in 10,000 it is 

 oppressive and almost intolerable. This has been supposed by some 

 to be due to a volatile poison exhaled from the lungs, for pure carbon 

 dioxide added alone in similar proportions to the air of a room has 

 not the same bad effect. Certain observers, indeed, alleged that the 

 condensed vapour of the breath, when injected into rabbits, produced 

 fatal symptoms. But this has been shown to be erroneous ; and the 

 most careful experiments have failed to detect in the air expired by 

 healthy persons any trace of such a poison. It has therefore been 

 suggested that the odour and other ill effects of a close room are due 

 to substances given off in the sweat and the sebum, and allowed by 

 persons of uncleanly habits to accumulate on the skin, and also to 



