THEORY OF DISEASE. 243 



It is evident that one and the same cause of disease 

 will produce in the organism very different effects, 

 according to the period of life ; and that a certain 

 amount of disturbance, which produces disease in the 

 adult state, may be without influence in childhood or 

 in old age. A cause of disease may, when it is added 

 to the cause of waste in old age, produce death (anni- 

 hilate all resistance on the part- of the vital force) ; 

 while in the adult state it may produce only a dispro- 

 portion between supply and waste ; and in infancy, only 

 an equilibrium between supply and waste (the abstract 

 state of health). 



A cause of disease which strengthens the causes of 

 supply, either directly, or indirectly by weakening the 

 action of the causes of waste, destroys, in the child 

 and in the adult, the relative normal state of health ; 

 while in old age it merely brings the waste and supply 

 into equilibrium. 



A child, lightly clothed, can bear cooling by a low 

 external temperature without injury to health ; the 

 force available for mechanical purposes and the tem- 

 perature of its body increase with the change of matter 

 which follows the cooling ; while a high temperature, 

 which impedes the change of matter, is followed by 

 disease. 



On the other hand, we see, in hospitals and chari- 

 table institutions (in Brussels, for example) in which 

 old people spend the last years of life, when the tem- 

 perature of the dormitory, in winter, sinks 2 or 3 de- 



