192 CONNEXION BETWEEN RESPIRATION 



heat occurs, and a return to the natural temperature 

 is an indispensable step towards recovery. 



The relation between the production of animal 

 heat, and the condition of the respiratory func- 

 tions, is the most direct and remarkable. In gene- 

 ral, other conditions being alike, heat is generated 

 more or less freely, in proportion to the size and 

 vigour of the lungs; and when these are impaired, 

 the production of heat is diminished. Hence many 

 persons with imperfectly developed lungs, and a 

 predisposition to consumption, complain habitually 

 of coldness of the surface and feet ; and many who 

 were previously in good health become more and 

 more sensible to cold, in proportion as the approach 

 of disease weakens the functions of the lungs. I 

 have noticed this increased sensibility to cold, as a 

 precursor of chronic pulmonary disease, both in my- 

 self and others, before any other very ostensible 

 symptom had appeared, and think I have seen its 

 farther progress arrested by the timely use of 

 proper means, where much greater difficulty would 

 have been experienced had the warning not been 

 attended to. 



The generation of heat in the living system being 

 so immediately connected with the lungs, we find 

 tjie temperature highest in those animals who pos- 

 sess them in the greatest perfection, viz. birds. In 

 many species, the internal heat exceeds that of man 

 by twenty or thirty degrees ; while that of man ex 

 ceeds, to as great an extent, the heat of such of the 

 inferior animals as are remarkable for imperfect or- 

 gans of respiration. 



The next condition affecting the production of 

 animal heat is the co-operation of the nervous sys- 

 tem. If the mind be depressed by grief, tormented 

 by anxiety, or absorbed in sedentary meditation, all 

 the bodily functions become weakened, the circula- 

 tion languishes, the breathing becomes slow and 

 scarcely perceptible, digestion is ill performed, and 



