542 TRANSACTIONS OF SECTION I. 



of blood to, and of tissue lymph which transudes from the blood vessels into, 

 each part of the body. The quality of the blood depends on the foodstuffs 

 digested and absorbed into it, and on the mutual interaction of the organs which 

 elaborate and purify the blood. The blood is circulated not only by the pumping 

 action of the heart but by each muscular movement and change of position, for 

 the valves are set cunningly in the veins, so that each and every movement sends 

 the blood swirling onward in its course. Above all, the breathing movements 

 forward the flow of blood from the organs of the belly to the heart. 



Now the activity of men engaged in sedentary indoor occupations depends 

 very largely on the temperature and humidity of the air. If the air is over 

 warm, windless and moist, we are slack, and losing less, we produce less heat. 

 So we come to eating less and breathing less. The organs of the body then 

 have a more restricted choice of building stones from which to elaborate the 

 blood, and the blood moves in more sluggish streams through the outlying 

 territories of our bodily world. Thus our first line of defence is weakened. 

 If the air is cool and moving we are braced up and are active, eat more and 

 breathe more. The blood is refined out of a large choice of foodstuffs, and the 

 organs receive an ampler supply of the rarer and more precious of the chemical 

 complexes — 'the building stones into which the digestive juices break down the 

 foods. More oxygen is taken in, the daily turnover of the body factory is 

 enlarged, and the blood which barters the rich merchandise of the organs one 

 with another moves in ampler and quicker streams. 



Our feelings of vigour and well-being depend, too, on the ceaseless in-flow 

 of sensations from the sense organs. Taking a great part in the conscious term 

 of these sensations are those from the skin. The cutaneous sense organs are 

 influenced by the temperature, and by the relative humidity of the air, which 

 controls the evaporation of moisture from the skin, and the passage of tissue 

 lymph from the blood into the skin, and this influence has potent effect on our 

 mental state. A warm, moist atmosphere brings much blood into the skin and 

 depletes the viscera which perfect the blood, and robs the brain of an ample 

 flow. The humidity and temperature of the air affects the mucous membrane 

 of the nose and respiratory air-way, and the evaporation from and flow of tissue 

 lymph through it, factors which must control largely both our comfort and 

 varying immunity to catarrhal infections. 



In battleships the great difficulty is to secure a good ventilation without 

 excessive cooling of the individual". The space is confined, and the men next 

 the ventilating orifices, feeling cold, shut them up. The conditions are such that 

 a man with tubercle bacilli in his sputum is very liable to infect others whose 

 natural immunity is deficient. .The mass influence of the dose must tell heavily 

 here. In small fishing-boats the men shut up the cabin and sleep in air in 

 which the lamp may finally go out from want of oxygen (less than 17 per cent.). 

 Men with tubercle ought at once to be weeded out of battleships. The introduc- 

 tion of the electric fan in India has increased the power of the European to 

 sleep and work beyond measure. I believe every employer and benefit society 

 would find it pay both in increased output of work and lessened loss from ill- 

 health, if every factory and workshop were brought below 60° F. and well 

 swept with currents of air. We accustom ourselves to live in rooms that are too 

 warm. 



I visited recently the Leo Road London County Council school, where every 

 room is swept with a gentle current of air at 57° to 60° F. by a plenum system. 

 The courteous headmaster told me the lost attendances from infectious diseases 

 were fewer than 1,000 per year, while in other schools they reach 10,000 and 

 more. The rooms felt cool and pleasant, and the children and masters anpeared 

 fresh at 4 r.M. The parents say the children eat more when they come to school. 

 Haldane has insisted on the necessity of paying attention to the wet-bulb 

 temperature in factories and mines. This applies also to ships. The wet-bulb 

 should not exceed 75° F., and must be kept below 70° F. For high wet-bulb 

 temperatures a better current of air must be supplied. I have enclosed half a 

 dozen students at a time in an airtight chamber containing about 3 cm. of air. 

 After about half-an-hour the CO, has risen to three or four per cent., and the 

 temperature has reached about 85° F. wet-bulb. The men are then very greatly 

 relieved by putting on electric fans in the roof, which whirl the stationary stale 

 air in the chamber and cool their bodies. 



