6o2 



NATURE 



[January 6, 192 1 



who could be placed in Grade 1. at the age of 

 eighteen years compared to the numbers who 

 could be placed in the same grade on being ex- 

 amined four or five years later " (Sir J. Galloway, 

 British Medical Journal, September ii, 1920). 



A second great cause of rejection was tuber- 

 culosis, much of which was unsuspected. Careful 

 statistics from one city revealed the striking fact 

 that of 277 cases proved to be tuberculous, 218, 

 or 78 per cent., were previously unknown to the 

 health authorities. 



Such being the state of affairs, the publication 

 of the second part of Dr. Leonard Hill's mono- 

 graph ' on the science of ventilation and open-air 

 treatment is particularly to be welcomed. Con- 

 taining much new work, the volume really com- 

 prises a series of essays reviewing the subject 

 from various points of view, both theoretical and 

 practical. The opening essay, in which Miss 

 D. Hargood-Ash collaborated, is devoted to the 

 physics of radiation, and presents the . recent 

 knowledge in regard to radio-active elements and 

 the electrotonic theory. The final chapter deals 

 with modern methods of ventilation and heating. 



For several years past Dr. Hill, in conjunction 

 with various colleagues, has been devoting his 

 attention to this question. According to the 

 popular notion, "stuffiness" and "closeness" of 

 the air are due to an excess of carbon dioxide in 

 the air, or to organic poisons from the breath. All 

 recent work goes to prove the falsity of these old 

 views. In regard to the latter hypothesis, all the 

 positive results so far recorded as to the poisonous 

 effects of the condensed moisture of the breath 

 can be explained on the assumption that either 

 the amount of condensed fluid injected into an 

 smimal was in itself sufficient to kill the animal by 

 virtue of its comparatively great volume, or that 

 the impurity arose from the protein of condensed 

 saliva. 



In regard to the carbon dioxide content of the 

 air, much money has been spent in keeping the 

 percentage of this gas down to the requirements of 

 the authorities, yet up to 3 per cent, of carbon di- 

 oxide in the air breathed produces no unpleasant 

 effects; with each breath it is a natural act t< 

 inspire the dead space air into the lungs, air 

 which in itself contains about 3 to 4 per cent, of 

 carbon dioxide. Indeed, the partial pressure of 

 carbon dioxide in the alveolar air is the normal 

 regulator of the respiratory act. Again, the ill- 

 effects of "stufhness" have nothing to do with 

 smell ; frequently those enduring the smell have 

 no idea of its presence or potency. 



It is now abundantly proved that the enervating 

 effects of close and confined atmospheres are due 

 to "heat stagnation" within the body. This is 

 particularly liable ^o occur when the wet-bulb 

 temperature is high, and efficient evaporation from 

 the skin through sweating prevented. The dis- 

 comfort under such conditions is alleviated by the 



* Privy Council. Medical Reierirch ("ouncil. " The Science of V«ntila- 

 tion and Open-air Treatment." Pan ii. Special Report Series, No. sa. 

 Pp. ?t)5. (London : H.M. Stationery Office, 1920). Price 6j. net. 



NO. 2671, VOL. 106] 



use of fans which stir up the air. One of the 

 most illustrative experiments in this direction is 

 that in which a number of persons were confined 

 in a hermetically sealed chamber in which a high 

 wet-bulb temperature was induced by means of 

 trays of water placed above electric heaters. At 

 the height of discomfort to those inside, people 

 outside the chamber could breathe the air without 

 ill-effects. Circulation of the air by fans in the 

 roof brought great relief to the occupants of the 

 chamber. 



The chemical purity of the air is important in so 

 far as it may give an indication of infective bac- 

 terial content, and in certain trades in which the 

 atmosphere becomes laden with dust particles, 

 particularly silica dust. It is also important from 

 the public point of view as regards the pollution 

 of the air by excessive coal consumption. Coal 

 consumption fouls the air with soot and smoke, 

 producing fogs which diminish sunlight, thereby 

 making cities dismal, and bringing loss of health 

 and happiness to the town dweller. Herein the 

 dweller in the country is at an advantage. Vital 

 statistics show that, despite all the sanitary ad- 

 vances of recent years, the town dweller is still 

 at a disadvantage as compared with the country- 

 man, who frequently lives in any but hygfienic 

 surroundings. The country dweller owes his rela- 

 tively robust health to many of the factors which 

 make for success in open-air treatment. 



The success of this treatment in tuberculosis 

 depends upon its judicious application. Exposure 

 to moving air induces efficient respiration, exalts 

 the metabolism, and lowers the fever. It must 

 be so employed that the bodily functions arc not 

 depressed and the heat-regulating capacity of the 

 individual exceeded. The patient must always 

 be happy and comfortable. As Dr. Hill puts it: 

 "The ideal conditions out of doors are seen to 

 promote the feeling of comfort and happiness, a 

 gentle cooling breeze to promote adequate cool- 

 ing of the skin and stimulate the metabolism of 

 the body, coolness and low-vapour tension of the 

 air to promote the evaporation of water from, and 

 blood-flow through, the respiratory membrane." 



The clothing of the body, in both health and 

 disease, should always be directed to the preven- 

 tion of heat stagnation. Many people greatly 

 overclothe. Clothes should be as light as possible, 

 permeable to air, allow free evaporation, and not 

 become wet with water vapour in such a way 

 that they cling to the skin and cause undue heat 

 loss and a feeling of "chilliness." Permeability 

 is essentially a matter of the method of weaving. 

 The cellular type of weaving is to be recom- 

 mended on this account for underclothing; 

 for outer clothing close-meshed fabric is also 

 to be avoided. Wool owes its advantage 

 in underclothing to the fact that the elas- 

 ticity of the hair keeps the garment off the 

 skin, thereby securing an air layer beneath, which 

 facilitates evaporation and prevents clinging wet- 

 ness. The less the adherence, the greater the 

 volume of entangled air, and the greater the heatr 



