24 



ABSORPTION. 



glands,* the moderns have more frequently 

 adopted the hypothesis of their vascular texture, 

 so that we may consider this doctrine as sup- 

 ported by the most recent and elaborate re- 

 se.irches.~f See LYMPHATIC; GLAND. 



2. T/ie question of venous absorption con- 

 sidered. We have now been describing those 

 organs, which are more specifically or appro- 

 priately termed the absorbent system, as being 

 those parts the office of which is confined to 

 this operation. But a very important and in- 

 teresting question must now be discussed, 

 whether the function of absorption is exclusive- 

 ly performed by the lacteals and the lymphatics. 



The ancient anatomists and physiologists 

 being unacquainted with the existence of the 

 lacteals and the lymphatics, yet observing the 

 evident effect of the operation of absorption, 

 ascribed these effects to the action of the veins; 

 and among the moderns, for some time after the 

 discovery of what were more appropriately 

 termed the absorbent vessels, it was still sup- 

 posed that the veins co-operated with them, 

 and in some cases were even the principal 

 agents. This was the universal doctrine until 

 the middle of the last century, and was one 

 of the points which was decidedly maintained 

 by Haller and his disciples.J 



The arguments by which the hypothesis of 

 venous absorption was supported may be re- 

 duced to two classes, partly of a physiological 

 and pathological, and partly of an anatomical 

 nature ; the first consisting of the results of 

 experiments performed for the express purpose 

 of investigating the subject, and of considera- 

 tions derived from the morbid conditions of 

 the system; the second depending more exclu- 

 sively upon anatomical considerations. The 



neck, but that they are not found connected with the 

 absorbents of the abdomen, and that they are en- 

 tirely wanting in fish and in the amphibia ; Phil. 

 Trans, for 1768, p. 217 et scq., and Enquiries, 

 pt. ii. ch. 4, 5, 6. We have the same statement 

 made by Monro. with respect to fish, p. 31. An- 

 tommarchi, on the contrary, asserts that birds, fish, 

 reptiles, and amphibia have " pochissime glrtii- 

 dule ;" Prod, delle grande anat. di Mascagni, p. 8 ; 

 but the statement is made in a general way, and 

 without reference to any particular observations. 

 It would appear that no specific apparatus for ab- 

 sorption has been discovered in any of the inverte- 

 bratrd animals. 



* We have the authority of Nuck, in favour of 

 the cellular structure, Adenologia, c. ii. p. 30 et 

 seq., fis. 9 . . 12 ; also of Cruikshank, c. 14 ; and of 

 Abemethy, Phil. Trans, for 1776, p. 27 et seq. 



t See Hewson, v. iii. c. 2. pi. 2; Werner and 

 Feller, Vas. Lact. and Lymph. Descript. tab. 2; 

 their figures, however, appear to be exaggerated ; 

 Ueclard, add. a Bichat, p. 231 ; Monro tert., Elem. 

 v. i. p. 558. On the lymphatic glands generally 

 see Haller, El. Phys. ii. 3. 16.. 27; Boycr, Anat. 

 t. iii. p. 243 . . 257 ; Mascagni, ps. i. sect. 5. p. 31 ; 

 Rullier, ubi supra, p. 120 et seq. ; Breschct, ubi 

 supra, p. 394. For plates of the glands, see Mas- 

 ragni, tab. 1. fig. 8... 12, tab. 2. fig. 4. . 8, tab. 4. 

 fig. 2. tab. 8, 16, 26; Cruikshank, pi. 3; Sheldon, 

 tab. 3, 5. 



t Boerhaave, Pralect. 103. and 247 ; Haller, 

 in not, 1. ad 106, Boerhaave, Prselect., and not. 1. 

 ad 245; also El. Phys. ii. 1.28; Monro secun- 

 dus, De Yen. .Lymph., p. 14. . 21 ; Walter, sur la 

 Resorption, Nouv. Mem. Berlin, pour 1786.. 7, 

 ct scq. ; Magcndic, Physio! . t. ii. p. 238. 



experiments referred to consisted in passing 

 injections from the veins to the absorbents, or 

 the reverse, thus proving;, as was supposed, 

 that a direct connexion subsisted between these 

 vessels. They were performed by the most 

 skilful anatomists of the age, and were gene- 

 rally acquiesced in, without either the accuracy 

 with which they were conducted, or that of the 

 conclusions deduced from them, being ever 

 called in question. Another class of experi- 

 ments consisted in passing ligatures round the 

 thoracic duct, so as to render it impervious to 

 the passage of the chyle, when it was supposed 

 that under these circumstances the nutrition of 

 the animal was not interrupted,* and the same 

 conclusion appeared to be substantiated by 

 various cases of natural obstruction of the duct, 

 or by certain malformations of the part, where 

 it was either defective, or did not convey its 

 contents, in the ordinary manner, into the 

 veins. The other set of arguments, which are 

 more purely anatomical, were derived from the 

 supposed fact that various parts of the body, 

 which were evidently subject to the operation 

 of absorption, were without lymphatics, and 

 that this was likewise the case with large classes 

 of animals, the general structure of which, as 

 far as regards their growth and nutrition, was 

 analogous to that of the mammalia. Admitting 

 these data, it seemed to be a necessary conse- 

 quence that absorption must in these instances 

 be performed by the veins, and hence it was 

 inferred that in all classes of animals, and in all 

 parts of the body, the veins co-operated with 

 the lacteals and the lymphatics in the function 

 of absorption. 



The doctrine of venous absorption was first 

 formally called in question, nearly at the same 

 time,f by Wm. Hunter and by Monro se- 

 cundus,J who, as it would appear, to a certain 

 extent, entered upon the investigation inde- 

 pendently of each other. The priority of dis- 

 covery in this, as in so many points connected 

 with anatomy, was for a long time the subject 

 of warm controversy. We may remark con- 

 cerning this question, that if the judgment of 

 the present age should incline to ascribe to 

 Hunter the original conception of the hypo- 

 thesis, it is also disposed to allow to Monro the 

 merit of establishing his opinion by a skilful and 

 laborious process of experiment and observation. 



The method which these illustrious rivals 

 adopted was, first, to repeat the experiments 

 of their predecessors, when, by noticing with 

 scrupulous accuracy all the circumstances con- 

 nected with them, they were able to demon- 

 strate, or at least to render it highly probable, 

 that in all those cases where injections had 

 passed between the absorbents and the veins, 

 either rupture or extravasation had taken place, 

 and that, when this was carefully guarded 



* Some experiments of this kind are referred to 

 by M. Majendie, as having been performed by M. 

 Dupiiytrcn, Physiol. t. ii. p. 167. See also Ri- 

 cherand, Elcmens de Physiologic par Berard. 



t Mediral Comment., passim ; Cruikshank, In- 

 trod.; Walter, 10 et seq. 



t Dissert, de' Sem. et Test, in Smellie, Thes. 

 t. ii. and De Ven. Lymph. Valv. 



