'54 



NATURE 



[October 3, 1912 



and can recommend the compressed-air bath as the 

 substitute for a bracing cold wind. 



The suilabiliiy of the clothing is of the greatest 

 importance, not only to the comfort but to the effi- 

 ciency of man as a worlcing machine, e.g. power of 

 soldiers to march. On a still day the body is con- 

 fined by the clothes as if by a chamber of stagnant 

 air. for the air is enclosed in the meshes of the 

 clothes and the layer in contact with the skin becomes 

 heated to body temperature and saturated with 

 moisture. 



The observations of Pembrey show that himself 

 and four soldiers, marching in drill order gn a 

 moderately warm day, lost more water and retained 

 more water in their clothes than on another similar 

 day when they worked with no jacket on. The 

 average figures were loss of moisture 1600, against 

 1200 grms., and water retained in clothes 254, 

 against 109 grms. With no jacket the pulse was, on 

 the average, increased 28 against 41 in drill order, 

 and rectal temperature 1° against V^° F. The taking 

 off of the jacket or throwing open of the jacket and 

 vest very greatly increase the physiological economy 

 of a march. It is absurd that on' a hot summer day 

 Boy Scouts should march with coloured scarves 

 knotted round their necks. Nothing should be worn 

 for ornament or smartness which increases the diffi- 

 culty of keeping down the body temperature. The 

 power to march and the efficiency of an army depend 

 on prevention of heart stagnation and avoidance of 

 fatigue of the heart. 



I conclude, then, that all the efforts of the heating 

 and ventilating engineer should be directed towards 

 cooling the air in crowded places and cooling the 

 bodies of the people by setting the air in motion bv 

 means of fans. In a crowded room the air confined 

 between the bodies and clothes of the people is almost 

 warmed up to body temperature and saturated with 

 moisture, so that cooling of the bodv bv radiation, 

 convection and evaporation becomes' reduced to a 

 minimum. The strain on the heat-regulating 

 mechanism tells on the heart. The pulse is 

 accelerated, the blood is sent in increased volume to 

 thc^ skin, and circulates there in far greater volume, 

 while less goes through the viscera 'and brain. As 

 the surface temperature rises, the cutaneous vessels 

 dilate, the veins become filled, the arteries may be- 

 come small in volume, and the blood-pressure low the 

 heart is fatigued by the extra work thrown upon it. 

 The mfluence of the heat stagnation is shown by 

 the great acceleration of the pulse when work is 

 done, and the slower rate at which the pulse returns 

 to its former rate on resting. 



The increased percentage ' of carbonic acid and 

 diminution of oxygen which has been found to exist 

 in badiv ventilated churches, schools, theatres, bar- 

 racks, is such that it can have no effect upon the 

 incidence _ of respiratory disease and higher death- 

 rate which statistical 'evidence has shown to exist 

 among persons living in crowded and unventilated 

 rooms. ^ The, conditions of temperature, moisture, 

 .■ind_ windless atmosphere in such places primarily 

 diminish the heat loss, and secondarilv the hea't 

 I)roduction. i.e., the activity of the occupants, to- 

 gether with total volume of air breathed, oxygen 

 taken in and food eaten. The whole metabolism of 

 the body is thus run at a lower plane, and the nervous 

 system and tone of the body is unstimulated by the 

 monotonous, warm, and motionless air. If hard 

 work has to be done it is done under conditions of 

 strain. The number of pathogenic organisms is in- 

 creased in such places, and these two 'conditions run 

 together— diminished immunitv and increased mass 

 influence of infecting bacteria. 



The volume of blood passing through, and of water 



NO. 2240, VOL. go"? 



vapour evaporated from, the respiratory mucous 

 membrane must have a great influence on the 

 mechanisms which protect this tract from bacterial 

 infection. While too wet an atmosphere lessehs 

 evaporation, a hot dry atmosphere dries up the 

 mucous membrane. As the immunising powers de- 

 pend on the passage of blood plasma into the tissue 

 spaces, it is clear that a proper degree of moisture 

 is important. The temperature, too, must have a 

 great influence on the scavenger activity of the ciliated 

 epithelium and leucocytes in the mucous membrane 

 of the nose. 



In the warm moist atmosphere of a crowded place 

 the infection from spray, sneezed, coughed, or spoken 

 out, is enormous. On passing out from such an 

 atmosphere into cold moist air the respiratory mucous 

 membrane of the nose is suddenly chilled, the blood- 

 vessels constricted, and the defensive mechanism of 

 cilia and leucocyte checked. Hence the prevalence of 

 colds in the winter. In the summer the infection is 

 far less. We are far more exposed to moving air, 

 and the sudden transition from a warm to a cold 

 atmosphere docs not occur. I believe that infec- 

 tion is largely determined by (i) the mass influence 

 of the infecting agent ; {2) the shallow breathing and 

 diminished evaporation from, and flow of tissue 

 lymph through, the respiratory tract, in warm, moist 

 confined air. Colds are not caught by exposure to 

 cold ^er se, as is shown by the experience of Arctic 

 explorers, sailors, shipwrecked passengers, &c. 



VVe have very great inherent powers of withstand- 

 ing exposure to cold. The bodily mechanisms be- 

 come trained and set to maintain the body heat by 

 habitual exposure to open-air life. The risk lies in 

 overheating our dwellings and overclothing our 

 bodies, so that the mechanisms engaged in resisting 

 infection become enfeebled, and no longer able to 

 meet the sudden transition from the warm atmosphere 

 of our rooms to the chill outside air of winter. The 

 dark and gloomy days of winter confine us within 

 doors, and, by reducing our activity and exposur' '^ 

 open air, depress the metabolism; the influenr v., 

 smoke and fog, gloom of house and streets, cave Ju 

 places of business and dark dwellings, intensif}' th . 

 depression. The immunity to a cold after an infec- 

 tion lasts but a short while, and when children re- 

 turn, after the summer holidays, to school and damp 

 chill autumn days, infection runs around. The his- 

 tory of hospital gangrene and its abolition by the 

 aseptic methods of Lister — likewise the history of 

 insect-borne disease — show the great importance of 

 cleanliness in crowded and much occupied rooms. The 

 essentials required of any good system of ventilating 

 are then (i) movement, coolness, proper degree of 

 relative moisture of the air; (2) reduction of the mass 

 influence of pathogenic bacteria. The chemical purity 

 of the air is of very minor importance, and will be 

 adequately insured by attendance to the essentials. 



.'\s the prevention of spray (saliva) infection by 

 ventilation is impossible in crowded places, it behoves 

 us to maintain our immunity at a high level. We 

 may seek to diminish the spray output of those in- 

 fected with colds by teaching them to cough, sneeze, 

 and talk with a handkerchief held in front of the 

 mouth, or to stay at home until the acute stage is past. 



In all these matters nurture is of the greatest im- 

 portance, as well as nature. .\ man is born with phy- 

 sical and mental capacities small or great, with inherited 

 characteristics, with more or less immunity to certain 

 diseases, with a tendency to longevity of life or the 

 opposite, but his comfort and happiness in life, the 

 small or full development of his physical and mental 

 capacities, his immunity and his longevity of life, 

 are undoubtedly determined to a vast extent by 

 nurture. 



