506 NUTRITION. 



fixes the standard, in a temperate climate, at 98. When we examine the temperature of 

 the hlood in the deeper vessels and note the variations in different parts, we shall see 

 that the axilla and the tongue, being more or less exposed to external influences, do not 

 exactly represent the general heat of the organism ; but these are the situations, particu- 

 larly the axilla, in which the temperature is most frequently taken, both in physiological 

 and pathological examinations. As a standard for comparison, we may assume that the 

 most common temperature in these situations is 98, subject to variations, within the lim- 

 its of health, of about 0'5 below and 1-5 above. 



Variations with External Temperature. The general temperature of the body varies, 

 though within very restricted limits, with extreme changes in climate. The results ob- 

 tained by Davy, in a large number of observations in temperate and hot climates, show 

 an elevation in the tropics of from 0'5 to 3. It is well known, also, that the human 

 body, the surface being properly protected, is capable of enduring for some minutes a 

 heat much greater than that of boiling water. Under these conditions, the animal tem- 

 perature is raised but slightly, as compared with the intense heat of the surrounding 

 atmosphere. According to the observations of Dr. Dobson, the temperature was raised 

 to 99*5 in one instance, 101 '5 in another, and 102 in a third, when the body was ex- 

 posed to a heat of more than 212. MM. Delaroche and Berger, however, found that 

 the temperature in the mouth could be increased by from 3 to 9, after sixteen minutes' 

 exposure to intense heat. This was for the external parts only ; but it is not at all prob- 

 able that the temperature of the internal organs ever undergoes such wide variations. 



It is very difficult to estimate the temperature in persons exposed to intense cold, as 

 in Arctic explorations, because the greatest care is always taken to protect the surface of 

 the body as completely as possible; but experiments have shown that the animal heat 

 may be considerably reduced, as a temporary condition, without producing death. In 

 the latter part of the last century, Dr. Currie caused the temperature in a man to fall 

 15 by immersion in a cold bath ; but he could not bring it below 83. This extreme 

 depression, however, lasted only two or three minutes, and the temperature afterward 

 returned to within a few degrees of the normal standard. The results of experiments 

 show that, while the normal variations in the temperature in the human subject, even 

 when exposed to great climatic changes, are very slight, generally not ranging beyond 

 two degrees, the body may be exposed for a time to excessive heat or cold, and the ex- 

 treme limits, consistent with the preservation of life, may be reached. As far as has been 

 ascertained by direct experiment, these limits are about 83 and 107. 



Variations in Different Parts of the Body.li is to be expected that the temperature 

 of the internal organs should be higher and more constant than that of parts, like the 

 axilla or mouth, more or less exposed to loss of heat by evaporation and contact with 

 the cool air ; and the differences observed in the blood in certain parts, as in the two 

 sides of the heart, have important bearings, as we shall hereafter show, upon the various 

 theories of animal heat. We shall here note the variations observed in the blood in dif- 

 ferent situations and confine ourselves to recent observations which have been made 

 with apparatus much more reliable and delicate than that which was formerly employed. 



It is universally admitted that the blood becomes slightly lowered in its temperature 

 in passing through the general capillary circulation ; but the amount of difference is ordi- 

 narily not more than a fraction of a degree. This fact is not at all opposed to the prop- 

 osition that the animal heat is generated in greatest part in the general capillary system, 

 as one of the results of nutritive action ; for the blood circulates with such rapidity that 

 the heat acquired in the capillaries of the internal organs, where little or none is lost, is 

 but slightly diminished before the fluid passes into the arteries, even in circulating through 

 the lungs ; and cutaneous evaporation simply moderates the heat acquired in the tissues 

 and keeps it at the proper standard. 



