686 ABSORPTION. 



partisans of lymphatic absorption, however, affirm that even if these 

 substances are met with in the veins, it by no means follows, that ab- 

 sorption has been effected by them; for the lymphatics, they assert, 

 have frequent communications with the veins; and, consequently, they 

 may still absorb and convey their products into the venous system. In 

 reply to this, it may be urged, that all the vessels arterial, venous, 

 and lymphatic appear to have intercommunication; but there is no 

 reason to believe, that the distinct offices, performed by them, are, 

 under ordinary circumstances, interfered with ; and, again, where would 

 be the necessity for these intermediate lymphatic vessels, seeing that 

 imbibition is so readily effected by the veins ? The axiom quod fieri 

 potest per pauca, non debet fieri per multa is here strikingly appro- 

 priate. The lymphatics, too, as we have endeavoured to show, exert 

 an action of selection and elaboration on substances exposed to them ; 

 but, in the case of venous absorption, there is not the slightest evidence, 

 that any such selection exists, odorous and coloured substances retain- 

 ing, within the vessel, the properties they had without. Lastly. Where 

 would be the use of organs of a distinct lymphatic circulation open- 

 ing into the thoracic duct, seeing that the absorbed matters might 

 enter the various venous trunks directly through these supposititious 

 communicating lymphatics; and ought we not occasionally to be able to 

 detect in the lymphatic trunks some evidence of those substances, which 

 their fellows are supposed to take up and convey into the veins ? 

 These carrier lymphatics have obviously been devised to support the 

 tottering fabric of exclusive lypphatic absorption, undermined, as it 

 has been, by the powerful facts and reasonings that have been adduced 

 in favour of absorption by veins. 



From the whole of the preceding history of absorption, we are of 

 opinion, that the chyliferous and lymphatic vessels form only chyle and 

 lymph, refusing all other substances, with the exception of saline and 

 other matters, that enter probably by imbibition, that the veins admit 

 every liquid, which possesses the necessary tenuity; and that whilst all 

 the absorptions, which require the substances acted upon to be decom- 

 posed and transformed, are effected by chyliferous and lymphatic 

 vessels; they that are sufficiently thin, and demand no alteration, are 

 accomplished directly through the coats of the veins by imbibition; and 

 we shall see that such is the case with several of the transudations or 

 exhalations. 



V. ACCIDENTAL ABSORPTION. 



The experiments, to which reference has been made, have shown, 

 that many substances, adventitiously introduced into various cavities, 

 or placed in contact with different tissues, have been rapidly absorbed 

 into the blood, without experiencing any transformation. Within cer- 

 tain limits, the external envelope of the body admits of this function; 

 out by no means to the same extent as its prolongation, which lines the 

 different excretory ducts. The absorption of drinks is sufficient evidence 

 of the activity of the function as regards the gastro-enteric mucous 

 membrane. The same may be said of the pulmonary mucous membrane. 

 Through it, oxygen and nitrogen pass to reach the blood in the lungs, as 



