Magendie on Jlhsorption. 297 



with which tliey are in contact. For instance, if a certain 

 quantity of ink be introduced into the pleura of a young 

 dog, in an hour's time the pleura, the pericardium, the in- 

 tercostal muscles, and the surface of the heart itself will be 

 sensibly tinged with black. (1) 



It appears then to be established beyond all doubt, that 

 all the blood vessels, whether arterial or venous, great 

 or small, in dead bodies or in living ones, possess in their coats 

 (parois) a physical property by which we may perfectly ex- 

 plain, and to which we may reasonably refer all the princi- 

 pal phenomena of absorption. To affirm that this property 

 is the sole cause which produces that effect would be going 

 beyond the limits assigned by sound logic ; but in the pres- 

 ent state of known facts, I am acquainted with none which 

 tend to invalidate this explanation ; on the contrary, they all 

 tend to confirm the exactness of it. 



For example, Lavoisier and Mr. Seguin have proved, by 

 a series of interesting experiments, that the skin, while cov- 

 ered by its epidermis, does not absorb water, nor any other 

 substance. But the epidermis is of a different nature from the 

 vascular membranes ; it is a sort of varnish which does not 

 imbibe, as every one may observe on his own body while 

 bathing; but as soon as the epidermis is taken off, the skin 

 absorbs like all other parts of the body, because the sides 

 of the vessels are then immediately in contact with the sub- 

 stances destined to be absorbed. Hence the necessity of 

 placing beneath the epidermis the substances to be absorbed 

 in innoculation and vaccination ; hence, also, the necessity 

 of long continued frictions ; and, often the employment of 

 greasy substances, to facilitate the absorption of certain 

 medicaments by the skin covered with its epidermis ; hence, 

 likewise, the preference given to those parts of the body 

 where the epidermis is thinnest for the application of medi- 

 caments by friction. 



1 will cite, as another example, the absorption which takes 

 place by all parts of our bodies of the most irritating sub- 

 stances, and even of substances which are capable of pro- 

 ducing chemical changes in our organization. This effect 

 is entirely opposed to the supposition that absorption is a 



(1) This effect is observable with still greater facility in pmallpr aTaimalf^. 

 such as rabbits, guinea piga, mice, &c. &c. 



Vpi,.ITI....No. 2. 38 



