ABSORPTION. *> 



of tetanus. If the circulation still exists, these phenomena 

 are produced much more quickly, because the motion of the 

 blood hastens the diffusion of the poison, without, however, 

 being indispensable to it : circulation is to absorption what 

 the movements in breathing is to the diffusion of the gases or 

 respiration. 



The vessels cannot thus, in the proper sense of the word, 

 be said to be absorbing organs : it is, properly speaking, the 

 fluids of the tissues, the blood itself, which absorbs. The 

 state of the blood has thus a great effect on the intensity of 

 the absorption. If the blood be saturated with water, as, 

 for instance, after an injection of water into the veins of an 

 animal, a fresh quantity of water will not easily penetrate. 

 Absorption is also very sluggish in the case of hydraarnia ; 

 and becomes very active, on the other hand, if the mass of 

 the blood be diminished (by bleeding), or if it has been 

 thickened, as, for instance, by purgatives or diuretics in the 

 case of the patients already mentioned. Similar experiments 

 have been made in regard to absorption of the fats. If the 

 blood is surcharged with fat (the normal proportion is 3 to 

 1000), the fatty substances ingested will be found nearly 

 entire in the alvine discharges, and scarcely any will be 

 absorbed. We may therefore say, in conclusion, that the 

 state of saturation or non-saturation of the blood is one of 

 those causes which have the most influence on absorption, in 

 regard to one substance or another. 



This diffusion, however, can take place only when the epi- 

 thelium which forms the barrier between the organism and 

 the fluids deposited on its surface permits and facilitates their 

 passage : the chief point of the study of absorption is thus 

 the attitude assumed by the intestinal epithelium during 

 these phenomena. 



In order to increase its points of contact with the matters 

 to be absorbed, the intestinal mucous forms numerous folds, 

 as the valvulcB conniventes, and especially the mill. These 

 are composed of a casing of columnar cells (Fig. 68), which, 

 as seen in front, appear as a sort of hexagonal flooring (free 

 base of the cell), while at the summit they are inserted in 

 the body of the villus (Fig. 69, A), and are in contact with 

 smaller cells, polyhedral or irregular, the germs of future 

 columnar cells (which are to these what the layer of Mal- 

 pighi is to the more superficial cells of the epidermis). The 

 central part, or body of the villus, is very complex (see Fig. 

 69, A and C). This is composed of an embryonic connective 



