ABSORPTION. 



33 



in them, that we are naturally led to conclude, 

 that they are destined for different uses, and 

 serve different purposes in the animal economy. 

 With regard to the lacteals, their use seems 

 to be clearly marked by their connexion with 

 the digestive organs, and by their contents, 

 as constituting the channel by which the chyle 

 is conveyed from the intestines to the thoracic 

 duct, and ultimately to the bloodvessels. We 

 cannot doubt that their primary function is to 

 supply the body with the elements which com- 

 pose the blood, and thus become the imme- 

 diate agents in its nutrition. Although, from 

 the experiments which have been related 

 above, it will appear that, on certain occasions, 

 the lacteals are not incapable of receiving 

 extraneous bodies, yet we may conclude, that 

 this is the case only under extraordinary cir- 

 cumstances, or in an unnatural state of the 

 parts. 



With respect to the lymphatics, their specific 

 use is less obvious. As their contents are ul- 

 timately mixed with those of the lacteals, we 

 may suppose that they contribute indirectly to 

 the nutrition of the body; but this would 

 appear not to be their primary, or even their 

 principal destination. Still we can scarcely 

 refuse our assent to the position, that absorp- 

 tion is the specific function of the lymphatics ; 

 and this will be equally the case, although we 

 may suppose that the veins cooperate with them 

 in this action. 



We are indebted to the genius of John Hun- 

 ter for a consistent or plausible theory of the 

 use of the lymphatics, which, with certain mo- 

 difications, is generally admitted to be correct. 

 Conceiving that the appropriate and specific 

 action of the lacteals is to nourish the body, 

 and to support the system by the addition of 

 new matter, that of the lymphatics is to mould 

 and fashion the body, to admit of the growth 

 and extension of the whole, while each in- 

 dividual part retains its proper form and 

 position. When we consider in what manner 

 an organized part increases in its dimensions, 

 we immediately perceive that it is not by mere 

 accretion, nor by simple distention; it is, on 

 the contrary, by an addition to every individual 

 portion, while they retain the same relation to 

 each other and to the whole. If we take the 

 case of a muscle, we find that each particular 

 fibre must be increased in length, so that the 

 distance may be augmented between the ten- 

 dinous extremities, while probably the number 

 of fibres that are contained in the membranous 

 covering is also increased ; the whole organ 

 consequently becomes larger in every one of its 

 individual parts, while they each retain their 

 former proportions and connexions.* 



We may apply the same train of reasoning 

 to the bones, which offer a still more remark- 

 able example of this change of form, inas- 



much as the firmness of their texture must 

 render it less easy to conceive of any alteration 

 in their dimensions and in the disposition of 

 their component parts. Here it is still more 

 obvious than in the case of the muscle, that 

 the change cannot be effected either by accre- 

 tion or by distention, but that a completely 

 new disposition of the integrant parts must 

 have taken place. The only means, however, 

 by which this can be accomplished is by the 

 former particles of the body being gradually 

 removed, and new ones deposited to supply 

 their place; the process being so gradual, that, 

 although the deposition of the new particle is 

 not precisely in the same situation with the 

 former, yet that of each particle is so nearly 

 so as to cause no obstruction or interruption 

 to the action of the organ. Now it is evident 

 that this removal of the old matter can be 

 effected by no process but by absorption, and 

 we may therefore conclude that the lymphatics, 

 either alone or in conjunction with the veins, 

 are the agents destined to perform this office. 



With respect to the actual nature of the con- 

 tents of the lymphatics there appears to be 

 some uncertainty. We have the analysis of 

 the fluid taken from the vessels of a dog by 

 M. Chevreul,* from which it would appear 

 that the lymph contains nearly the same in- 

 gredients with the blood, but diluted with a 

 much larger proportion of water. We must, 

 however, suppose that the fluid contained in 

 the lymphatics will vary very considerably in 

 its composition, according to the part of the 

 body from which it is taken, or the condition 

 of the same part at different times; yet we are 

 scarcely able to detect an actual state of things 

 which altogether corresponds with what we 

 might have been led to expect would have been 

 the case.f It may indeed be presumed that 

 in the ordinary condition of the system, the 

 process by which the parts of the body are 

 absorbed is so very gradual, that the change in 

 the chemical constitution of the lymphatic 

 fluid is as inconspicuous as the change in the 

 organs from which it is absorbed, and that it 

 is only in morbid cases, where there is some 

 extraordinary quantity of matter to be re- 

 moved, that we should expect to be able to 

 detect it in the lymph. And this, to a certain 

 extent, agrees with the fact ; for when the ab - 

 sorbents are called into action to remove col- 

 lections of pus, or when they become the 

 vehicles of any poisonous or morbid body, 

 the substance in question has been occasionally 

 found in them. 



The doctrine of the removal or absorption of 

 all the parts of the body is rendered evident by 

 a variety of cases, in which any particular 

 organ or texture is broken down or removed, 

 merely by cutting off the supply of fresh matter. 

 It is upon this principle that we explain the 



* See Winterbottom, de Vas, Absorb, in Smel- 

 lie's Thcs. Med. t. iv. ; also Cruikshank, p. 108, 9. 

 For the more recent views of physiologists on the 

 subject the reader is referred to Adelon, art. 

 " Absorption," Diet, des Scien. Med. t. i. 



VOL. I. 



* Magendie, Elem. t. ii. p. 171, 2. 



t Magendie, Elem. t. ii. p. 196, 7, et alibi. 

 Mascagni, however, states that the lymph varies 

 according to the parts to which it is contiguous, 

 ps. 1. . 4.; see also Blumenbach, $. 438. 



D 



