148 THE LAWS OF ORGANIC 



by the liberal expansion of leaves ; and how often 

 with anxiety does he look forward to the fall of 

 snow to protect the tender plant. His observa- 

 tions, although unenlightened by a knowledge 

 of those principles on which the effects depend, 

 are valuable, as they are in accordance with views 

 proposed to explain the nature of those principles. 



CLIX. If we take a view of the animal eco- 

 nomy at this period, in which vegetation dis- 

 plays its precocity, we shall observe that its more 

 perfect systems are equally exposed to, and in- 

 jured by the sudden change from heat to cold. 

 The warmth of spring is a stimulus to the sur- 

 face of the body and the functions of the lungs. 

 The blood, that was previously concentrated to 

 the more vigorous capillary vessels, becomes now 

 diffused among the most minute, making the 

 extremities and external parts of the body near- 

 ly as warm as the internal, which is never the 

 case during the severity of winter. 



The distribution of the blood having under- 

 gone this alteration preparatory to the fervid and 

 uniform days of summer, is checked by the cold 

 nights of spring ; from which cause, catarrhs, in- 

 flammations, and fevers are produced as in au- 

 tumn. The only difference between these two 

 seasons is, that autumn acts upon the system by 

 repressing too violently the conditions of the cir- 

 culation derived from summer, while spring, 

 having changed too early thje circulation charac- 



