LECT. IV. IMBIBITION AND TRANSMISSION. 81 



animals, consists not merely of the imbibition of a liquid by 

 a tissue, but also of the passage into the blood-vessels of 

 the liquid with which such tissue is in contact. It is at the 

 blood that the absorbed matter ought to arrive ; this is the 

 final object of the phenomenon. Let us distinguish, then, 

 two things in absorption : the introduction of the substance 

 to be absorbed through the interstices of an organized body, 

 and its subsequent passage into the circulation. 



It is easy to demonstrate the existence of the first part of 

 this function. Here is a frog, whose inferior extremities 

 only, have been immersed for several hours in a solution of 

 ferrocyanide of potassium. If we remove the animal from 

 the liquid, carefully wash it with distilled water, and then 

 cut it in pieces, we can easily prove that the solution has 

 penetrated into every part. Wherever we touch the viscera 

 or tissues with a glass rod moistened with a solution of the 

 chloride of iron, a more or less deep blue stain is pro- 

 duced. 



I shall the more insist on this manner of demonstrating 

 the reality of absorption, because it explains to us very 

 clearly the two parts of which we have stated this function 

 to consist. If a living frog be immersed, by its inferior ex- 

 tremities only, in a solution of ferrocyanide of potassium, 

 and the animal soon after killed, we can scarcely detect 

 any traces of the salt in the muscles of the legs and thighs ; 

 whereas the heart and lungs give very distinct evidence of 

 it when they are touched with chloride of iron. 



One experiment more, and the conclusion will be evi- 

 dent. I immerse another frog, which has been dead for 

 some minutes, in the same solution, and leave it there for 

 the same time that I did the other. When tested, the lungs 

 and heart offer no greater evidences of the presence of the 

 ferrocyanide than does any other part of the body. 



Here is the explanation of these experiments : The solu- 

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