ABSORPTION AND EXHALATION. LiECT. IV. 



LECTURE IV. 



ABSORPTION AND EXHALATION IN ANIMALS AND PLANTS. 



ARGUMENT. Absorption in animals consists of two acts, imbibition and 



transmission. All vessels absorb ; proofs that blood vessels absorb ; 



proofs that the lymphatics and lacteals absorb. Physical conditions of 



absorption. Laws of absorption. 

 Exhalation; its mechanism similar to that of absorption. Transformations 



effected during absorption and exhalation. 

 Absorption in plants; summary of facts concerning it. The movement of 



the juices of plants inexplicable by capillarity and imbibition merely. 



Sponglets. Evaporation or transpiration by the leaves. The ascent of 



liquid in plants depends on both the root and leaves. 



THE preceding lectures on the phenomena of capillarity, 

 imbibition, and endosmose, have been delivered principally 

 for the purpose of preparing you for the study of absorption 

 and exhalation. It is not for me to speak of the researches 

 that have been made expressly for the purpose of determin- 

 ing on which of the various organs these functions especially 

 devolve. In treatises on physiology, you will find them 

 exclusively ascribed sometimes to the veins, sometimes to 

 the lymphatic vessels. 



We find it difficult to account for so many discussions 

 when we reflect on the structure of all these different tissues, 

 and on the necessary existence of the phenomena of absorp- 

 tion and exhalation in a large series of the lower animals 

 apparently devoid of lymphatic vessels. 



Absorption in Animals consists of Imbibition and Trans- 

 mission. Absorption, considered as a function of living 



