130 



The radicles from which the lymphatics arise, have orifices so very 

 minute, that they are imperceptible to the naked eye; a tolerably accu- 

 rate notion may be formed of them, by comparing them to the puncta la- 

 chrymalia, which are larger and more easily discovered. Each orifice 

 endowed with sensibility, and with a peculiar power of contraction, di- 

 lates or contracts, absorbs or rejects, according as it is affected by the 

 substances which are applied to it. The variations of the absorbing pow- 

 er, according to the age, the sex, the constitution, and different periods 

 of the day, show that it cannot be compared, as several physiologists have 

 clone, to that principle which makes fluids ascend, contrary to the laws 

 of gravitation, in capillary tubes. If absorption were a process merely 

 mechanical, it would, in no case, be accelerated or retarded, and would 

 proceed with a regularity never observed in the vital functions. The 

 mouth of every lymphatic, when about to absorb, erects itself, draws 

 towards itself, and raises the surrounding membranous parts, and thus 

 forms a small tubercule similar to the puncta lachrymalia. These little 

 bulgings deceived Lieberkuhn, and led him to think, that the absorbents 

 of the intestines, originated from small ampullalae, or vesicular enlarge- 

 ments, which, as so many exhausted receivers, pumped up the fluid ex- 

 tracted from the food*. This physiologist may, further, have been led 



they should be endowed with that peculiar sensibility which requires the existence of 

 nerves. The bones are active by being subject to the process of nutrition, but in 

 every other respect, they are absolutely passive. In the opinion of some people, such 

 doctrines are real discoveries. Credat judxus Jipella,^ non ego. Author's Note. 



* As to the precise manner in which absorption is effected, physiologists are not 

 agreed. By some it is contended, that it is entirely the result of capillary attraction. 

 To the exercise of this species of affinity, three circumstances seem only to be de- 

 manded : 



1. The tube must not exceed a certain size. 



2. It must be of an equal calibre throughout. 



3. One of its extremities must be immersed in a fluid. 



Notwithstanding what has been urged to the contrary, capillary attraction unques- 

 tionably is influenced neither by the flexibility of the tube, nor its position. It is now 

 perfectly well ascertained, that the operation goes on whether the tube be soft or hard, 

 or whether it be placed vertically, horizontally, or obliquely. 



These facts being admitted, and also, that the lymphatic vessels are within the di- 

 mensions necessary to capillary attraction, which they undoubtedly are, the hypothesis 

 referring absorption to this principle, does not, at first view, strike us as altogether un- 

 reasonable. When examined, however, more clearly, it will be found liable to all the 

 embarrassments enumerated in the text, and to others of not less weight. 



Two additional objections at once occur to us. 



1. Did the absorbents act mechanically, as is alleged, they would take up indiscri- 

 minately all fluids presented to their mouths, instead of which, they exercise a degree 

 of selection amounting almost to fastidiousness. 



2. The absorbents have not that mechanism which capillary attraction requires. 

 They frequently swell or bulge out in their course, and become of irregular capaci- 

 ties. Even at their orifices they assume the figure of the funnel, commencing with an 

 exceedingly minute opening, which suddenly expands. Aware of the unfavourable- 

 ness of the structure to the progression of fluids, it has been maintained by some other 

 of the advocates of capillary attraction, that the fluid is simply imbibed by the power of 

 this principle, and afterwards propelled by the united force of muscular pressure, and 

 the action of the contiguous arteries. 



We do not think the hypothesis at all improved by this modification of it. We be- 

 lieve, that in absorption there is no capillary influence, or, indeed, any sort of extrinsic 

 agency employed. It seems to us to be owing altogether to the inherent contractile 

 power of the vessel, and bears no very remote analogy to the peristaltic action of the 

 intestines. We will, however, in a few words, explain our meaning more distinctly. 



When chyle, or any appropriate fluid, is applied to the mouth of an absorbent, it is 



