552 PRACTICE OF PHYSIC. 



situde, or sudden and considerable change of temperature from 

 heat to cold. 



XCV. The circumstances of persons rendering them more 

 liable to be affected by cold, seem to be, 1. The weakness of 

 the system, and particularly the lessened vigour of the circula- 

 tion, occasioned by fasting, by evacuations, by fatigue, by a last 

 nights debauch, by excess in venery, by long watching, by much 

 study, by rest immediately after great exercise, by sleep, and by 

 preceding disease. 2. The body, or its parts, being deprived of 

 their accustomed coverings. 3. One part of the body being 

 exposed to cold, while the rest is kept in its usual or a greater 

 warmth. 



X.CVI. The power of these circumstances (XCV.) is de- 

 monstrated by the circumstances enabling persons to resist cold. 

 These are, a certain vigour of constitution, exercise of the body, 

 the presence of active passions, and the use of cordials. 



Besides these, there are other circumstances which, by a dif- 

 ferent operation, enable persons to resist cold acting as a sensa- 

 tion, such as, passions engaging a close attention to one object, 

 the use of narcotics, and that state of the body in which sensi- 

 bility is greatly diminished, as in maniacs. To all which is to 

 be added, the power of habit with respect to those parts of the 

 body to which cold is more constantly applied, which both di- 

 minishes sensibility, and increases the power of the activity gen- 

 erating heat. 



XCVII. Beside cold, there are other powers that seem to be 

 remote causes of fever ; such as fear, intemperance in drinking, 

 excess in venery, and other circumstances, which evidently 

 weaken the system. But whether any of these sedative powers 

 be alone the remote cause of fever, or if they only operate 

 either as concurring with the operation of marsh or human ef- 

 fluvia, or as giving an opportunity to the operation of cold, are 

 questions not to be positively answered : they may possibly of 

 themselves produce fever ; but most frequently .they operate as 

 concurring in one or other of the ways above mentioned. 



u I shall not decide whether fear of itself ever produces fever ; 

 but, concurring with miasmata and contagion, it may certainly 

 .prove a very powerful exciting cause. Thus, it may act in 



