HUMAI PHYSIOLOGY. 



BOOK FIRST. 



STATICAL PHYSIOLOGY, 



CONDITIONS OF LIFE. 



CHAPTER I. 



Conditions of Life. Nature and Sources of Substances supplied to the Body. Annual Quantities 

 required. Table of Physiological Standards. Animals do not create, but transform Substan- 

 ces. Properties and Quantities of Matters received by the System. Properties and Quantities 

 of those it restores. Heat of the Body arises from Combustion. Cooling Agencies in an An- 

 imal. Necessity of Repairs in the System. Physical Aspect of Man. The SouL The Vital 

 Principle. Importance of Physical Science to Physiology. 



FOR the maintenance of the life of man three chemical conditions must 

 be complied with. He must be furnished with air, water, and combusti- 

 ble matter. 



Under the same conditions, also, all animals exist. Even in those 

 which seem to furnish us with instances of departure from this Three condi- 

 general rule, the exceptions are rather apparent than real. To tions oflife - 

 breathe, to drink, to eat, are the indispensable requisites of life. If there 

 be among insects some which seem never to take water, or among fishes 

 some which never taste solid food, these peculiarities disappear as soon 

 as we understand them properly. Where a high development has been 

 attained, as in man, experience assures us that the same inevitable result 

 awaits a cessation of respiration for a few moments, an abstinence from 

 water for a few hours, or from food for a few days. 



The supply of a part of these necessaries of life is adjusted to the ur- 

 gency of the want. The act of breathing is incapable of de- Sources of sup- 

 lay, but the air is accordingly every where present, and al- ply of material, 

 ways fit for use. We can bear with thirst for a little time, and the earth 

 here and there furnishes her springs and other stores of water. But far 

 otherwise is it in the obtaining of food. It is the lot of all animals to 

 secure nourishment by labor, and even of men the larger proportion, both 



