PHYSICAL BIOCLIMATOLOGY 
body is not capable of supplying sufficient water to 
make f = 1. This is known to occur in hot deserts, that 
is, wind no longer produces cooling. The average person 
is rarely capable of filtering more than 1 kg hr ~ of 
water through the skin; in certain morbid conditions, 
for instance prior to heat prostration or after prolonged 
thirst, the rate of filtering is even less. The subsequent 
overheating is associated with desiccation of the skin 
and the formation of a salt crust. 
Since f as well as #; represents a physiological vari- 
able, the total effect of Ja, 3,, ea, and v can be de- 
termined only by calculations of the type referred to 
above, but hardly by means of instruments which 
seek to simulate actual conditions. The problem of 
defining climatic strain in one unit becomes even more 
difficult in the case of sunshine (S > 0). A solution of 
this problem seems more promising in the region be- 
tween sultriness and cold. 
Cooling. Perspiration (f > 0) is an emergency func- 
tion of the body; @, values should stay between certain 
limits. We feel comfortable when 3, % 33C and f 
= 0, that is, when a = 0.2 and 6 = 26.4 (equation 
(8a)). This corresponds to an effective temperature of 
approximately 22C, which is the ‘summer comfort” 
standard of the American Society of Heating and Ven- 
tilating Engineers for lightly clothed persons. For a 
= 0.2, the effect of atmospheric humidity on skin 
temperature is already negligible; however, values of 
relative humidity above 70 per cent and below 20 per 
cent are undesirable for secondary reasons (effect on 
clothing and microorganisms, or desiccation of the skin, 
respectively). If the last term (evaporation) is omitted 
and 3 = 0, equation (7) can be used to derive a 
numerical criterion describing the total effect of several 
climatic elements in one index: 
1. Température résultante [58] and operative temper- 
ature [38]. These quasi-temperatures comprise the radi- 
ation and air temperature if S = 0 and v = 0: 
h,O+Nao Va 
h, aF hao 
2. Cooling power. The problem here is to determine 
the (artificial) heat supply Q@ of a device required to 
keep its temperature 3, constant (usually at 34C). 
The quantities «, «, Mx/Fa, and the constants of 
equations (1) to (8a) are supposed to have the 
values corresponding to those of the human body. 
Instruments of this type are the katathermometer of 
L. Hill and the frigorimeter of C. Dorno (see [13, 16, 
69, 74, 80)). 
3. Standard operative temperature. Calculation [38] 
permits the comparison of two rooms (v = 0, S = 0), 
considering the skin temperature #, constant: 
(9) 
op. temp. = 
h,d, + haDa a Os(ha om ho) 
fhe JE Mig 
4. Cooling temperature (9). This is the fictitious skin 
temperature of a sphere, heated with @ = const, whose 
constants correspond to those of a blond human. In 
this case, 
std. op. temp. = (10) 
1115 
o. as h,d, + ha Da ar Q/Fa AF €WS/4 
: hy, + he : 
The value (# — 12C) is the “temperature of equal 
effectivity,’ that is, the temperature of a ‘normal 
room” (v = 0, S = 0, 3 = 8,), which is physiologically 
equivalent. (For existing instruments by Pfleiderer and 
Buettner [13, 16, 69, 80] the constants are Q/F = 
96 Cal m” hr’, ex = 0.60, « > 0.90, and d = 15 
em (sphere).) For an additional, smaller model, the 
“Frierkoerper”: Q/F = 120 Calm” hr’, d = 7 cm 
[19]. 
Numerous other forms may be reduced to those 
given above. We give cooling temperature preference 
over cooling power and standard operative temperature, 
since in the mean cooling range the human body tends 
to achieve a constant Q with variable 3,, rather than 
to keep 3, constant. 
The purposes of establishing and observing these 
combination elements are as follows: 
1. Establishment of a comparative physiological 
climatology for nonhumid regions. The thermal load 
on a human body may be calculated from the elements 
v, 0, Ja, and S, if these are known at the location of 
the body; unfortunately, this is rarely the case. On the 
other hand, series of cooling measurements are available 
only sporadically. 
2. Evaluation of artificial climate and clothing (see 
below). 
3. Determination of the dosage for exposure to the 
open air in sanatoriums in moderate and cool climates. 
The tonic effect of the change from indoors to a veranda 
increases with the deviation from the comfort climate 
and with the duration of outdoor exposure. The 0, 
value recorded by the frigorigraph serves as a measure 
of comfort or load; values are to be measured at the 
patient’s bed or calculated by means of equation (11); 
3; = 37C is comfortable. A formula found successful in 
a sanatorium on the North Sea coast (calculated from 
data in [68]) is 
(11) 
(|o — 87 |)t = BD, (12) 
where ¢ is the exposure time in minutes, B = 8 for 
3, < 35C, B = 20 for & > 40C, and t = 4D for 35C 
< 3 < 40C. The dose D increases from 5 for hyper- 
sensitive persons to 60 for healthy persons. Because of 
possible damage from ultraviolet radiation, the exposure 
time must be limited on the basis of special measure- 
ments or tables (see Table II). 
Clothing. The main purpose of clothing is to produce 
a bearable skin temperature through thermal insulation. 
Let us assume that the incident radiation S is ab- 
sorbed at the surface of clothing having a temper- 
ature #,; outside, jj = #,; underneath the clothing, 
which has the thickness d, the skin temperature @, 
prevails. The quantity h, is the “thermal conductance” 
of the fabric and 1/h, is its “insulation value” (as a 
measure of this, one also uses 1 Clo = 1.715 deg C 
m’ hr Cal‘). The values of h, and h, are practically the 
same for clothed and for bare sections except perhaps 
in the case of thickly clothed fingers. The increase of 
the surface area has to be taken into account. In the 
