43 



artificial circumstances, some of which have a powerful ten- 

 dency to depress the vital tonicity of the hody. Man is the 

 only animal universally distributed over the earth, and his 

 constitution possesses a greater degree of flexibility and 

 power of adapting itself to variety of climate than that of 

 any other animal. In establishing himself in every part of 

 the earth, or even in maintaining himself in the part in 

 which he may have been born, he is often placed in very 

 artificial circumstances, which have the effect of diminishing 

 the tone and vigour of the body — some of them by requiring 

 great exertion of the bodily or mental powers ; others by 

 removing him partially from the operation of some of the 

 natural stimulants which are so essential to health — such 

 as pure air, light, &c, whilst others, again — such as the 

 depressing mental emotions, and long continued cold, pro- 

 duce the same effect by depressing the vigour of the functions. 

 Now I maintain that in all these circumstances the expe- 

 rience of mankind has proved that the moderate use of 

 stimulants is beneficial. The vital power of tonicity, which 

 is thus liable to be depressed, is that property of the animal 

 economy which gives to the bodily frame, and especially the 

 muscular parts, their strength and firmness. The constitu- 

 tion of every individual possesses this vital power of tonicity 

 in a greater or less degree, and it is powerful and fluctuates 

 little in those who are healthy and vigorous. In weak 

 persons it is less powerful, and subject to greater fluctua^ 

 tions. It is lowered by privation of the natural stimuli — 

 such as pure air and proper food, and by the depressing 

 mental emotions — such as grief. It is especially depressed 

 during typhus fever; and, in this disease, it frequently sinks 

 until it becomes entirely extinguished. 



4th, From observing that certain medicines have the 

 power of raising the vital power of tonicity, and that their 

 action is similar to that of alcoholic stimulants. The class 

 of medicines which possess this power have been called 

 tonics. Quinine and the preparations of iron are examples. 

 The action of tonics is stimulant ; but it differs from that of 

 alcoholic stimulants, in being exerted slowly and almost 

 imperceptibly — in being more pennanent, and in being 

 followed by very little depression ; so that, by frequent 

 repetition, a continued stimulant effect is maintained, which 

 restores the exhausted tone of the system. The exciting 

 mental emotions — such as joy and hope — are powerful 

 tonics, as they cause continued excitement without subse- 

 quent depression. As the stimulant action of tonics is so 

 slight, and at the same time so enduring, I would give them 



