910 SPECIAL PHYSIOLOGY. 



of blood. The large vessels connected with the heart and lungs, are 

 collapsed and empty. The gall-bladder is distended with bile, and the 

 neighboring parts are much colored with this fluid, from post-mortem 

 transudation. In some cases, the eyes are open, and exhibit an intense 

 red color, as if they had been highly inflamed, resembling what is some- 

 times seen in persons who have died from exposure to cold. Decom- 

 position of the whole body quickly takes place. 



The time that a Man can live without food has been variously esti- 

 mated. It is generally supposed that a healthy person, deprived of 

 both solid and liquid food, would die in from seven to ten days. Cases, 

 however, are on record of men who have lived more than three weeks, 

 without touching solid food. 



DYNAMICS OF THE HUMAN BODY. 



The chemical processes continually occurring in the nutrition and 

 waste of the living animal body, throw light upon many other phe- 

 nomena which take place in it. Besides these vito-chemical processes, 

 it exhibits various dynamic acts, viz., purely dynamic, as in the per- 

 formance of certain internal and external mechanical work, by nervo- 

 muscular action ; thermic, as in the evolution of animal heat ; electric, 

 as exemplified in the currents of electricity which constantly play 

 through all living nervous and muscular substance, and in the more 

 powerful discharges of the electric fishes ; and lastly, photic, illustrated 

 by the evolution of light in the lower animals. The living animal body 

 is, according to this view, a machine, in and by which certain physi- 

 cal work is performed. 



In the Inorganic world, chemical, dynamic, thermic, electric, and 

 photic phenomena are also continually occurring. They are always 

 manifested in connection with certain changes in the condition of a 

 material substratum, or matter, and modern physicists have arrived at 

 the conclusion, that, however different these phenomena may be from 

 each other in their outward manifestation, they may be referred, not 

 to a different force in each case, but to correlated forces, or to one 

 force or energy, capable of acting in many convertible modes. Each 

 mode of manifestation of force has been experimentally shown to be 

 capable of giving rise to the others, or rather of changing into them; 

 for it disappears in so doing, and equivalent quantities of those other 

 modes of action are then called into play. Thus, for example, arrested 

 mechanical motion, or friction, produces a proportionate quantity of 

 heat; whilst heat, in the expansion of water into steam, gives rise to 

 motion. Chemical action, in the explosion of gunpowder, produces 

 motion, heat, and light, and doubtless also electrical phenomena, whilst 

 the moving cannon-ball develops heat as it strikes the target. Elec- 

 tricity also will give rise to chemical action, motion, heat, and light, 

 and so on. Heat and all these other actions are modes of motion, 

 either of the masses or of the molecules of matter. In the various 

 conversions of one into the other, there is neither loss nor production, 

 but merely a transmutation of force. 



In the Organic world, similar manifestations of force occur : chemi- 



