288 ABSORPTION. [CHAP. xxvi. 



general indications of the lines in which further investigation may 

 be pursued with advantage. 



Applying them to the mechanical arrangements provided in the 

 living animal for this function, it is plain that they have a nearer 

 reference to the capillary blood-vessels than to the lymphatics. In 

 both we have a simple membrane of extreme thinness, through 

 which the absorbed fluid has to pass, and in doing so it must neces- 

 sarily obey those laws which form the proper subject of experi- 

 mental physico-chemical inquiry. But in the blood-vessels, the 

 fluid on the side towards which absorption tends is already in motion 

 by a mechanical force, the heart's action, and the absorption is 

 accompanied with a contrary current of exosmose ; whereas in the 

 lymphatics, the internal fluid appears to have no motion but what 

 is derived from the same force on which the endosmose depends, 

 and we have no evidence of any outgoing current. In these re- 

 spects the absorbents resemble more nearly than the capillaries, the 

 spongioles and absorbent vessels of plants. 



Function of the Absorbents. A few words may be added on the 

 use of the absorbents in the oeconomy. The chyliferous vessels 

 probably have the same office for the intestinal tissues as the 

 lymphatics in other parts ; but besides this, they are largely de- 

 veloped, and specially adapted by their mode of origin on the 

 mucous surface, to take up a portion, at least, of the food, after it 

 has been rendered capable of absorption by the action of the pan- 

 creatic secretion. This portion appears to be pre-eminently the 

 fatty or oily, which, as far as experiments and observation have 

 yet determined, is almost exclusively absorbed by the lacteals. It is 

 chiefly in containing so much more fat that chyle differs from lymph. 



The lymphatics cannot yet be said to have their office at all 

 definitively ascertained, yet it is not difficult to assign them a part 

 with some degree of probability. It appears that they form an 

 interlacement among the capillaries in the interstices of most of the 

 organs and tissues of the body, and contain a fluid not dissimilar in 

 kind from the liquor sanguinis, though more dilute. They cannot 

 be engaged in distributing new material to the organism, because 

 their structure adapts them only for removing fluid from the tissues, 

 and pouring it into the blood-vessels, and because the current 

 within them is unequivocally in that one direction. Thus the fluid 

 they contain must enter them from the interstices of the tissues, 

 having been ultimately derived either directly from the capillaries, 

 or indirectly from them through the tissues. It seems not im- 

 probable that the liquor sanguinis effused through the capillary 



