AND OF THE VEINS. 621 



1. That the circulation of sap in plants,* and of 

 blood through many of the lower animals which 

 have no heart, is active during summer, checked 

 by cold nights, and wholly arrested during win- 

 ter : 2. That the circulation of chyle through 

 the lacteals, and of lymph through the absorbents, 

 is obviously independent of the heart's action ; 

 and like that of the blood, is in proportion to 

 the healthy temperature of animals; being more 

 rapid in birds than in mammalia ; languid in 

 cold blooded animals ; and suspended in all by 

 intense cold, or by arresting the supply of ca- 

 loric by respiration : 3. That after decapitation 

 and removal of the heart from rabbits, or placing 



* I have been told that caloric cannot be the cause of circula- 

 tion in plants, because the sap rises more rapidly in spring than 

 summer, which is true enough. But this is owing first, to the empty 

 state of their vessels and pores, induced by the long absence of sap ; 

 and secondly, to its rapid expenditure in the formation of leaves 

 and flowers, on first beginning to rise. For the same reason, 

 when the lacteal absorbents have been completely emptied by 

 fasting, they take up chyle more rapidly than when in a state of 

 repletion ; while it is certain that when dry, the earth absorbs 

 water far more rapidly by capillary attraction, than when satu- 

 rated by repeated heavy rains. The above objection is therefore 

 without any solid foundation. Nor has it ever been proved that 

 the capillary circulation of animals is owing to contraction of 

 their minute vessels. And it has been observed by Wedemeyer, 

 that when they were made to contract by the injection of alcohol 

 or vinegar into them, the flow of blood through them was retarded. 

 The only view then which seems capable of explaining the phe- 

 nomenon, is that of an attraction between fluids and solids, 

 whether we call it capillarity, endosmose, exosmose, vital affinity, 

 or by any other name. 



