300 



TEMPERATURE AND HUMIDITY 



from loss of sodium chloride. It is, there- 

 fore, the custom to provide salt tablets for 

 men who do heavy work under such condi- 

 tions. The same procedure was followed 

 during the war with troops in the tropics. 

 In the early days of steam, temperatures 

 in the furnace rooms of naval vessels in the 

 tropics sometimes passed 65°C, with high 

 relative humidity. In 1909 and 1910 the 

 attack rate for heat stroke in the Navy was 

 about 8 per 1000, and between 1861 and 

 1911, there were 20 deaths and 33 men in- 

 valided from this cause. Severe cramps and 

 muscle twitchings attributed to local drying- 

 out of the tissues and accumulation of waste 

 products of metabolism are among the pro- 

 nounced symptoms of heat stroke, and the 

 body temperature may be so completely 

 upset that temperatures of 40° to 44°C have 

 been recorded, associated, of course, with 

 profound hazard to life. 



TABLE X 



Mean Rectal Temperatures of Clothed 



Subjects after 4-8 Hours Exposure to 



Room Temperatures Between 20°-30°C 



Air Temperature. . . 

 Relative Humidity. 

 Rectal Temperature . 



30° 

 80% 

 37.4' 



Relation of Thermal Conditions to Human 

 Comfort 



Even within the range of reasonably effec- 

 tive thermal adaptation, and long before 

 extreme strain occurs, there are certain defi- 

 nite physiological changes which may have 

 significant effects on human comfort. The 

 basic studies of the New York State Com- 

 mission nearly a quarter of a century ago 

 yielded the following results. 



The rectal temperature, when subjects 

 came to the laboratory in the morning, 

 showed a definite relation to the outdoor 

 temperature of the preceding night in the 

 summer season (but not under the artificial 

 conditions of winter Hfe in heated houses). 

 The mean rectal temperature, after 4-8 



hours exposure to experimental conditions 

 (subjects normally clothed with moderate 

 activity) is given in Table X. 



No difference in blood pressure was noted 

 among the three atmospheric conditions de- 

 fined above. A special experiment at 38°C 

 with 87 percent relative humidity showed a 

 definite increase in systolic pressure. A 

 comparison of changes in diastolic pressure 

 with changes in the product of the pulse rate 

 showed that the resistance in the peripheral 

 portion of the circulatory system was de- 

 creased in the warmer conditions. 



Particularly interesting results were ob- 

 tained with regard to a factor known as the 

 Crampton Index, which is one of many rela- 

 tive measures of the efficiency of cardiac and 

 circulatory adjustments to various stresses. 

 This index is based on the ratio between in- 

 crease in heart rate and rise or fall of blood 



TABLE XI 



Changes in the Crampton Index of Vasomotor 



Response to Postural Change in Clothed 



Subjects at Temperatures Between 



20°-30°C 



Air Temperature. . . 

 Relative Humidity. 

 Crampton Index 



30° 



80% 



34 



pressure when the subject passes from a 

 reclining to a standing position. It meas- 

 ures, in an approximate manner, the effec- 

 tiveness and economy of adaptation to the 

 extra burden of erect posture and is pre- 

 sumably a function of vasomotor reaction. 

 The scale on which the Crampton Index is 

 expressed is so designed that a figure of 100 

 corresponds to an increase of 10 millimeters 

 of blood pressure with an increase of less than 

 4 beats in the heart rate; a value of zero cor- 

 responds to a decrease of 10 millimeters of 

 blood pressure with an increase of over 40 in 

 the heart beat. The values given in Table 

 XI were recorded in the Commission experi- 

 ments. Higher values of the index noted at 

 20°C are considered as indications of better 

 circulatory adjustment to the gravity stress 

 of the erect posture. Since such substantial 



