448 OF ABSORPTION AND SANGUIFICATION. 



It has been found that, after bathing in infusions of madder, rhubarb, and 

 turmeric, the urine was tinged with these substances ; and that a garlic plaster 

 affected the breath, when every care was taken, by breathing through a tube 

 connected with the exterior of the apartment, that the odor should not be re- 

 ceived into the lungs. 1 Gallic acid has been found in the urine, after the external 

 application of a decoction of a bark containing it; and the soothing influ- 

 ence, in cases of neuralgic pain, of the external application of cherry-laurel 

 water, is well known. Many saline substances are absorbed by the skin, 

 when applied to it in solution ; and it is interesting to remark that, contrary 

 to what happens in regard to the absorption of these from the alimentary canal, 

 they are for the most part more readily discoverable in the Absorbents than in 

 the Veins. This is probably due to the fact that the imbibition of them takes 

 place entirely according to physical laws; in conformity with which they pass 

 most readily into the vessels which present the thinnest walls and the largest 

 surface. In the intestines, the vascular plexus on each villus is far more exten- 

 sive than the ramifying lacteal which originates in it ; and as the walls of the 

 veins are thin, there is considerable facility for the entrance of saline and other 

 substances into the general current of the circulation : but in the skin, the lymph- 

 atics are distributed much more minutely and extensively than the veins; and 

 soluble matters, therefore, enter them in preference to the veins. The absorbent 

 power of the lymphatics of the skin is well shown by the following experiments. 

 A bandage having been tied by Schreger round the hind-leg of a puppy, the limb 

 was kept for twenty-four hours in tepid milk ; at the expiration of this period, 

 the lymphatics were found full of milk, whilst the veins contained none. In 

 repeating this experiment upon a young man, no milk could be detected in the 

 blood drawn from a vein. It has been shown by Miiller that, when the posterior 

 extremities of a frog were kept for two hours in a solution of prussiate of potass, 

 the salt had freely penetrated the lymphatics, but had not entered the veins. 

 It does not follow, however, from these and similar experiments, that in all 

 tissues the lymphatics absorb more readily than the veins ; for as the capillary 

 bloodvessels in the lungs are much more freely exposed to the surface of the 

 air-cells than are the lymphatics, we should, on the principles just now stated, 

 expect the former to absorb more readily. This appears from experiment to be 

 the fact; for, when a solution of prussiate of potass was injected by Mayer into 

 the lungs, the salt could be detected in the serum of the blood much sooner than 

 in the lymph, and in the blood of the left cavities of the heart, before it had 

 reached that of the right. 



471. Our inferences with regard to the ordinary functions of the Lymphatic 

 system, however, must be rather drawn from the nature of the fluid which it 

 contains, and from the uses subsequently made of it, than from such experi- 

 ments as the preceding. We shall presently see, that there is a close corre- 

 spondence in composition between the Chyle of the Lacteals, and the Lymph of 

 the Lymphatics; the chief difference being the presence of a considerable quantity 

 of fatty matter in the former, and of a larger proportion of the assimilable sub- 

 stances (albumen and fibrin) which are equally characteristic of both ( 474). 

 This evident conformity in the nature of the fluid which these two sets of vessels 

 transmit, joined to the fact that the fluid Lymph, like the Chyle, is conveyed 

 into the general current of the circulation, just before the blood is again trans- 

 mitted to the system at large, almost inevitably leads to the inference, that the 

 lymph is, like the chyle, a nutritious fluid, and is not of an excrementitious 

 character, as maintained by Hunter and his followers. 3 On the other hand, the 



1 Prof. Dunglison's Human Physiology," 7th edit. vol. i. p. 688. 



2 Since the time of Hunter, who first brought prominently forwards the doctrine alluded 

 to, it has been commonly supposed (in this country at least) that the function of the Lymph- 



