34 



ABSORPTION. 



removal of a part by pressure. If a muscle, or 

 even a solid bone be exposed to constant pres- 

 sure, by which its nutritive arteries are ob- 

 structed, it will be gradually diminished in 

 bulk, and at length completely abstracted. 

 And this is frequently effected by the action of 

 a body much softer than the substance which 

 is removed, as, for instance, we observe a bone 

 to be absorbed by the pulsation of a blood- 

 vessel, or the growth of a fleshy tumour.* 



But although we may venture to affirm that 

 this moulding of the body, or rather of its in- 

 dividual parts, is effected by the lymphatics, 

 either alone or in conjunction with the veins, 

 there is considerable difficulty in forming a 

 distinct conception of the mode in which they 

 operate. The operation cannot, strictly speak- 

 ing, be mechanical, nor have we any evidence 

 of the existence of a chemical solvent, by 

 which the parts may be reduced to a liquid 

 state, so as to fit them for entering into the 

 mouths of the vessels. We may conceive of 

 the source of supply being cut off by pressure 

 or in other ways, but still we are at a loss to 

 account for the mode in which the solids are 

 either dissolved or broken down, so as to adapt 

 them to the process of absorption. There is, 

 however, one principal or general fact in the 

 animal economy, which will probably some- 

 what assist us in our inquiry, viz. that it appears 

 to be essential to the well-being, or even to the 

 existence of the corporeal frame, that all the 

 materials of which it is composed should un- 

 dergo a constant change. It appears that these 

 materials, after a certain length of time, expe- 

 rience some alteration in their nature, by which 

 they are rendered unfit for the further perform- 

 ance of their functions as constituents of the 

 living body. They are therefore removed and 

 are replaced by fresh matter, this interchange 

 being brought about in the gradual manner 

 which was described above. Now this process 

 implies a constant decomposition of the parts 

 of the body, and as this decomposition is 

 effected particle by particle, it may not be un- 

 reasonable to conjecture, that each particle, 

 when it ceases to form an integral part of an 

 organ, is left in a state proper for being taken 

 up by the absorbents. But independent of any 

 hypothetical views of this description, we may 

 assume it as a probable conclusion, that the 

 configuration and moulding of the body is the 

 specific and appropriate office of the lymphatics, 

 while its nutrition is effected more immediately 

 by the lacteals. 



With respect to the lymphatic glands we 

 have seen above that their structure is involved 

 in considerable obscurity, and we may remark, 

 that their use is at least equally obscure. Among 

 other opinions that have been entertained on 



* For the absorption of the solids, see Monro on 

 the Brain, c. 5; also Blumenbach, . 436; and 

 Bell's Anat. vol. iv. p. 311, 2. Kibes, who is a 

 zealous defender of the doctrine of venous absorp- 

 tion, remarks that the absorption of the bones must 

 be effected by the veins, because they are not fur- 

 nished with lymphatics ; Mem. Soc. d'Emulation, 

 t. -viii. p. 621. 



the subject, some physiologists have supposed 

 that the glands are proper secreting organs, 

 which are destined for the purpose of preparing 

 a peculiar substance that is mixed with the 

 chyle and the lymph, or that they merely serve 

 the mechanical purpose of mixing together more 

 completely the constituents of the fluid that is 

 contained in the vessels, and thus produce 

 some change in its nature or consistence.* 

 There do not appear to be any arguments, either 

 anatomical or physiological, by which this point 

 can be decided ; but we may remark, that 

 while the number and mode of distribution of 

 these glands in the mammalia would seem to 

 point them out as performing some important 

 office in the animal economy, their rarity in 

 birds and fishes proves that they are not essen- 

 tial to the existence of most of the functions of 

 animal life, nor have we any mode of explaining 

 the cause why they should be more necessary 

 to the mammalia than to the other classes, 

 which in many of their functions so nearly re- 

 semble them. 



It only remains for us to offer a few remarks 

 on the connexion between the function of ab- 

 sorption, and the other vital actions of the 

 system, especially with the two leading princi- 

 ples of contractility and sensibility. We have 

 already had occasion to remark on the con- 

 nexion of absorption with muscular contracti- 

 lity, and although it may be difficult, or even 

 impossible, to demonstrate the muscular fibres, 

 or to exhibit any apparatus of this description, 

 by which the action of the vessels can be ac- 

 counted for, st. 11 we have strong reason for 

 supposing that the absorbents possess this 

 power, and that it is the main cause by which 

 their contents are propelled. 



With respect to the relation which subsists 

 between the nervous and the absorbent systems, 

 we are induced to suppose, both from anato- 

 mical and from physiological considerations, 

 that it is merely of an indirect nature. From 

 the researches of the anatomists, we learn that 

 there are few nerves sent to the absorbent vessels 

 or glands, and that even these seem rather to 

 pass by them, in order to be transmitted to 

 some other organs, than to be ultimately des- 

 tined for the use of the absorbent system. The 

 action of the mouths of the lacteals, or the 

 power by which they are enabled to take up 

 the substances that are afterwards transmitted 

 along them, is involved in much obscurity, as 

 is likewise the case with the power which these 

 vessels seem to possess of changing the nature 

 of their contents. Both of these have been re- 

 ferred to the nervous influence, but this has 

 been done in that loose and general way, which 



* On this subject we may refer to Haller, El. 

 Phys. ii. 3. 25; Blumenbach, Inst. Phys. . 425, 

 442; Ilicherand, Elem. p. 153; Mascagni, ps. i. 

 sect. 5. p. 33 ; Magendie, Elem. t. ii. p. lb'6, 201 ; 

 Chaussier et Adelon, ubi supra, p. 278. Rullier, 

 art. " Inhalation," in Diet. Sc. Med. ; Meckel, 

 Manuel, sect. 6. ch. i. ; Adelon, art. " Lymphatique 

 (Physiologic), " Diet, de Med. t. xiii, also art. 

 " Chyliferes," ibid. t. v. p. 239; Desgenettes, 

 Journ. Med. t. xc. p. 322, et seq. 



