AND INSENSIBLE PERSPIRATION. 61 



mulated during winter, offers a much better solution, 

 either with respect to the animal or vegetable consti- 

 tution. For the same reason, it is necessary to apply 

 warmth very slowly and carefully to persons frozen, or 

 even chilled only, by a more than usual degree of cold, 

 which renders them more susceptible of heat, and a 

 temperate diet and very moderate stimulants are most 

 safe and useful to the unexhausted constitutions of chil- 

 dren. The same principle accounts for the occasional 

 flowing of the sap in autumn after a slight frost. Such 

 a premature cold increases the sensibility of the plant 

 to any warmth that may follow, and produces, in a 

 degree, the same state of its constitution as exists after 

 the longer and severer cold of winter. Let me be al- 

 lowed a further illustration from the animal kingdom. 

 Every body conversant with labouring cattle must have 

 observed how much sooner they are exhausted by the 

 warm days of autumn, when the nights are cold, than 

 in much hotter weather in summer, and this is surely 

 from the same cause as the autumnal flowing of the 

 vegetable sap. 



The sap, or lymph, of most plants when collected 

 in the spring as above mentioned, appears to the sight 

 and taste little else than water, but it soon undergoes 

 fermentation and putrefaction. Even that of the Vine 

 is scarcely acid, though it can hardly be obtained with- 

 out some of the secreted juices, which in that plant are 

 extremely acid and astringent. The sap of the Sugar 

 Maple, Acer saccharinum, has no taste, though ac- 



E2 



