Adjustment a Continuous Process 157 



dividual variation, so that some of us are consistently warmer 

 or cooler than the normal. Moreover, in the case of any 

 particular individual, the temperature is constantly fluctuat- 

 ing with the variations in external and internal conditions. 

 It is not everybody who can get into a fever heat through 

 trivial aggravation, but everybody does raise the temperature 

 of his blood through muscular exertion or emotional strain. 



The output of heat incidental to increased activity of all 

 sorts would become a source of injury to the living matter 

 of the body if the mechanism for maintaining a fairly uni- 

 form temperature were not as effective as it is. The increased 

 consumption of oxygen made necessary by increased activity 

 is made possible by accelerated breathing and heartbeat. 

 Everybody knows that running around the block results in 

 more rapid breathing and more vigorous heart action and 

 more copious perspiration. We commonly assume that the 

 need for more oxygen and for the more rapid removal of the 

 carbon dioxid and for preventing an excessive increase in tem- 

 perature somehow brings about these suitable modifications in 

 the behavior of our organs. A lowering of the temperature 

 somehow leads to a closing of the pores, and a reduction of 

 perspiration. Variations in the composition of our food bring 

 about variations in the proportions and quantities of the vari- 

 ous juices that take part in digestion. 



The invasion of the body by foreign bodies such as bac- 

 teria produces highly specialized reactions on the part of 

 the white corpuscles of the blood and probably also on the 

 part of other tissues (see page 61). The automatic re- 

 flexes in which the nervous system participates are commonly 

 recognized as purposeful. The contraction of the pupil of 

 the eye with increasing illumination, the blinking of the 

 eyelids on the approach of minute particles, the withdrawing 

 of a limb in response to injury, the increased flow of saliva in 

 response to stimulation of the taste organs of the mouth and 

 so on, are familiar examples of adjustive reactions. The in- 

 ternal organs, as well as the externally visible structures, are 

 also constantly changing in many details as part of the process 



