Source of Motions upon the Earth. 309 



of force ; for when this is lost — when the physical forces exceed 

 those of life, or contrariwise, — it is inconceivable that there can be 

 health. The absolute energy of both the classes may be conceived, 

 in different places, to be greater or less, without necessarily pro- 

 ducing abnormal action, if in their increase or diminution they 

 preserve the same proportion between themselves. The absolute 

 energy, again, of the several forces belonging to each class, may in 

 different places vary, and still health exist, if the whole combined 

 power of both classes are duly proportioned to each other. But if the 

 whole power of the vital and solar forces is greater or less than the 

 whole amount of the physical forces, it may be expected that the 

 actions of life will either be performed with an energy and vifdence 

 tending to the destruction of the living beings, or else that they must 

 directly come to a stop. In tropical countries, the vital and che- 

 mical actions of the body take place with more energy than they do 

 in temperate climates, as was formerly mentioned, and as we may 

 infer from the greater rapidity of the growth of the body, and of its 

 dissolution and decomposition after death. If, however, the two 

 counterbalance each other, health may be preserved ; but in conse- 

 quence of their straining against each other, or from the state of 

 tension in which they are held, the equilibrium will be somewhat 

 unstable, and if one of them gives way, even to a small degree, the 

 other will be apt quickly to gain the mastery. Hence, perhaps, the 

 violence and rapidity of many tropical diseases. It seems to me 

 not improbable, that in those sorts of fever to which the terms of 

 typhoid, malignant, or putrescent, are applied, we have examples of 

 the forces of life being depressed, or acting with insufficient power 

 against the chemical and the external forces, and of a consequent 

 tendency to the subjugation of life, and to a direct descent to death. 

 What diseases illustrate the opposite condition, — that in which the 

 vital forces are augmented, or act in undue attivity to the physical 

 and chemical forces, — whether some of those termed inflammatory 

 are of this sort or not, — cannot with anything like certainty be 

 said. 



If there be truth in this doctrine, we should expect that vegetable 

 life, and the lives of the lower animals, will at times be affected in 

 a manner analogous to that of man. Possibly we see somewhat of 

 this in the fact, that many epidemic diseases affecting man, are ac- 

 companied by derangement in vegetable life also, and that disease 

 and mortality frequently prevail, at the same time, among the cattle, 

 and the lower animals. Thus, scanty harvests, mildews — " causino- 

 vegetables, corn, and fruit, to become black and corrupt," — cattle 

 dying, "horses, oxen, and cows, with rotten tongues, sheep and hon^s 

 with their hoofs dropping off, and calves with rotten ears," are not 

 unfroquent concomitants of some epidemic diseases. We have other 

 illustrations of the same thing in what Dr Mead states, of it 



