COLD AND HEAT 705 



distinctly noticeable in congested areas. If the application 

 is very severe or long continued, the vessels lose their tone, 

 become paralyzed, and we have passive congestion, inflam- 

 mation, and finally death. 



Ordinarily, reaction sets in aftor the use of cold, more 

 particularly if followed by heat, when an active hypersemia 

 is substituted for the ischssmia. This is brought about both ' 

 by reflex stimulation of the heart by the cold, and local dila- 

 tion of the vessels. Therefore, when we wish to constringe 

 parts, we use moderate cold continuously ; but, by alternat- 

 ing cold and heat we may accelerate the blood h-upply, and 

 by first forcing out, and then bringing back the fiuids of the 

 tissues, we can maintain such an activity of the circulation 

 that even solid exudations are absorbed. Cold, locally, 

 lessens nervous irritability and pain directly, and, also, by 

 contracting the afferent vessels, it diminishes the impact of 

 the blood on sensitive parts. Moderate heat is said, never- 

 theless, to produce much the same result by relaxing the 

 capillaries of the collateral circulation, thus draining off the 

 blood and relieving tension in the inflamed part. Tissue 

 change is diminished, locally, by the action of cold. Sup- 

 puration and sloughing proceed but slowly under its retard- 

 ing influence. Acute abscess is converted into what might 

 be logically termed a "cold abscess" in the most literal 

 sense of the word. Bendotely, moderate cold applied to the 

 body for a short period actually increases general tempera- 

 ture by stimulating reflexly the heat centres, increasing 

 oxidation and lessening radiation from the contracted super- 

 ficial vessels. If cold is in contact with the whole body for 

 a longer time, the temperature gradually sinks and the 

 reduction continues for some hours, when, in healthy ani- 

 mals, the temperature rises above normal. Such effects are 

 much more pronounced in pyrexia. The action upon the 

 nervous system is exceedingly important therapeutically. 

 The most powerful stimulating action is exerted upon the 

 centres of innervation controlling the circulatory, respira- 

 tory, digestive and excretory organs. In fever, this treatment 



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