ANATOMY. 



OROAXS 0V 



The absorbents are a minute kind of 

 vessels found in aninr.il bod'u-s, which at- 

 tract and imbibe any fluid that is brought 

 near their mouths. They are so minute 

 and transparent, as not to be discovered 

 in ordinary dissection ; but by great la- 

 bour they have at length been detected in 

 great numbers in every tribe of animals. 

 As these vessels are transparent, their 

 contents are visible, which circumstance 

 occasioned them to receive the different 

 denominations of lactealsand lymphatics. 

 The former were so called, because they 

 imbibed 'he chyle, a mi Iky fluid, from the 

 bowels; whilst the latter, containing much 

 lymph, which they had taken up from all 

 the interstices of the body,were therefore 

 named lymphatics. The discovery ofthis 

 M of vessels is referred to the seven- 

 teenth century. But at first their number 

 did not appear sufficient to perform the 

 whole function of absorption ; neither had 

 they been discovered in birds or fishes, 

 whence anatomists still retained the idea 

 that the veins participated in this impor- 

 tant office. The merit of first demonstra- 

 ting 1 the absorbing vessels in those animals 

 belongs to Mr Hewson, who assisted in 

 the labours of the first eminent anatomical 

 school in London, where anatomy was 

 most ably taught by Dr. Hunter. And it 

 is to the immortal Hunter that we arc in- 

 debted for fully proving the important 

 doctrine, that the whole business of ab- 

 sorption isperformedby the vessels which 

 we are now considering. They have of 

 late been injected in such great abun- 

 dance, that they appear fully adequate to 

 perform their office. 



If. as we firmly believe, these vessels be 

 the only ones which perform the office of 

 absorption, they must exist in even' part 

 of the body. For there is no spot on the 

 surface of the skin from which ointment 

 may not be taken up, nor any internal 

 part from which blood, when accidentally 

 effused, may not be absorbed; nay, the 

 very matter composingthe texture of our 

 bodies is undergoing continual removal 

 and renovation. These vessels must there- 

 fore be supposed tobeginby open orifices 

 generally throughout the body, although 

 the fact can be demonstrated in the intes- 

 tines only. On the inner surfaces of these 

 organs they appear to the unaided eye 

 tine and pointed tubes : but by the mi- 

 croscope theirmouths are discerned to be 

 patulous, and like a cup. The beginning 

 absorbents soon join together, and after 

 some time form minute vessels, capable of 

 being injected by anatomists : these again 



conjoin, and form larger vessels, which 

 are still discoverable with great diffi- 

 culty. 



In *' ructure and arrangements these ves- 

 sels have great similitude to veins : they 

 have in consequence been namedby some 

 anatomists the lymphatic veins. Like the 

 veins, their sides are thin and transparent, 

 thoxigh of considerable strength : like the 

 veins, they frequently communicate toge- 

 ther, or, as it is technically termed, anas- 

 tomose. The advantage derived from 

 these communications is obvious : for by 

 these means, the dissimilar matters which 

 they take up from various parts are mix- 

 ed together, and blended with the lymph, 

 which they imbibe from the intersticesof 

 the body, and which serves as the vehi- 

 cle for such heterogeneous particles ; 

 . they also prevent accidental pressure 

 made on a few vessels from obstructing 

 the progress of the absorbed fluids, which 

 are in that case convoyed forwards by 

 collateral channels. Like the veins also, 

 these tubes, by conjoining, form a tube of 

 smaller area than the united areas of the 

 vessels before their junction. The effect 

 of this construction is the same as in the 

 veins ; that is, an acceleration in the cur- 

 rent of the lymph, in proportion as it 

 conies nearer to the trunk of the absorb- 

 ing vessels. The diameter of the thoracic 

 duct bears but a small proportion to the 

 united diameters of all the minute ab- 

 sorbents in the body, and when this duet 

 has been opened, the lymph has flowed 

 from it with a force and jet like that with 

 which the blood issues from a large vein. 

 Like the veins, the absorbents are furnish- 

 ed with numerous valves, which prevent 

 any retrograde motion of their fluids, and 

 also prevent any portion of the vessel 

 from sustaining the weight of more fluid 

 than is contained between its valves. The 

 absorbents, however, differ from the veins 

 in one very material circumstance, TIZ. 

 that thev have a power of contraction, 

 and are able of themselves to propel their 

 contents. Whoever reflects on the phe- 

 nomena of absorption can scarcely doubt 

 that these vessels have a contractile pow- 

 er, by which they refuse admission to 

 noxious substances, whilst they readily 

 imbibe those that are salutary. If these 

 vessels are observed in the mesentery, 

 when turgid with absorbed chyle, their 

 contents will disappear in a certain tract, 

 and again become visible ; a phenomenon 

 that can only be explained by supposing 

 the vessel to contract at that part, and 

 urge forwards its contents. Haller found 

 that the thoracic duct contracted when 

 stimulated, so that there can be little 



