26 



ABSORPTION. 



and by various pathological considerations. 

 Of these authors, one of the first, both in 

 point of time and of ability, is M. Magendie, 

 whose opinions on this subject, connected as 

 as they are with some of those of his most 

 distinguished countrymen, have been brought 

 forward in a form which entitles them to the 

 fullest and most respectful attention. 



Of the two sets of observations by which 

 Hunter and Monro attempted to establish their 

 hypothesis respecting lymphatic absorption, 

 those derived from the analogy of the lacteals 

 may still be considered as maintaining their 

 ground ; while the conclusion which they de- 

 duced from their experiments has been called 

 in question, partly because it was thought not 

 to be the legitimate inference from the experi- 

 ments, and partly in consequence of the ex- 

 periments themselves having been conceived 

 to be imperfect or incorrect. It is principally 

 upon the latter ground that the force of the 

 objections has been rested ; and it has been, 

 first, by repeating the experiments of Hunter, 

 and afterwards by varying them in different 

 ways, that their insufficency has been attempted 

 to be proved. It has been stated above that 

 the main support of the doctrine of the ex- 

 clusive action of the lacteals and the lymphatics 

 was derived from those experiments of Hunter, 

 in which it appeared that, when the circum- 

 stances were the most favourable for the re- 

 ception of substances into the veins of the 

 mesentery, they could not be proved to have 

 entered these vessels ; and hence it was con- 

 cluded that the veins did not, under any cir- 

 cumstances, possess the power of absorption. 



We are informed, however, by M. Magendie 

 that experiments have been performed by him- 

 self and by M. Flandrin, which afforded directly 

 contrary results, and that these experiments 

 were so frequently repeated, and varied in 

 such a manner, as to leave no doubt of their 

 accuracy.* We have here the opposing testi- 

 mony of individuals, both of them of the 

 highest authority in science, and eminent for 

 their skill in experimental research. From 

 personal considerations it might be difficult, 

 if not impossible, to decide between them ; 

 but when we take into account the circum- 

 stance that the experiments of MM. Magendie 

 and Flandrin were executed subsequently to 

 those of Hunter, and with the benefit of his 

 experience and that of the improved state of 

 the science during the last half century ; when, 

 moreover, we are informed that the experiments 

 of the French physiologists were more nu- 

 merous than those to which they were opposed, 

 and that their results were uniform and un- 

 equivocal, we can scarcely refuse our assent 

 to the conclusion, that the experiments of John 

 Hunter do not afford a sufficient foundation 

 for the doctrine of the non-absorption of the 

 veins. 



But the French physiologists have not sa- 

 tisfied themselves with repeating the experi- 

 ments of Hunter; they have extended them 



* Physiol. t. ii. p. 181 et seq. ; Journ. Med. 

 t. Ixxxv. p. 372 et seq., and t. Ixxxvii. p. 221. 

 et seq., and t. ex. p. 73 et seq. 



in various ways, and have obtained results 

 supposed to be still more decisive in favour 

 of venous absorption. Among the most im- 

 portant, or at least the most curious of these, 

 is an experiment which was performed by 

 M. Magendie, in conjunction with M. Delille, 

 and which was conceived by these physiolo- 

 gists to afford the most unequivocal proof of 

 their hypothesis. It consisted in dividing all 

 the parts of one of the posterior extremities 

 of a living animal except the artery and the 

 vein, and in applying to the foot a poisonous 

 substance ; when, in the short space of a few 

 minutes, the effects of the poison on the func- 

 tions of the animal were most distinctly ap- 

 parent.* It was argued that in this case there 

 was no mode of communication by which the 

 poison could be conveyed from the extremity 

 to the centre of the system except the vein, 

 and that, therefore, the vein must have acted 

 as the absorbing vessel. The experiment was 

 rendered more striking, and, as was conceived, 

 more conclusive, by dividing the bloodvessels 

 themselves and introducing metallic tubes 

 between the divided ends, through which alone 

 the two currents of the arterial and venous 

 blood respectively could pass in forming the 

 communication between the extremity and the 

 trunk of the animal, yet, under these appa- 

 rently unfavourable circumstances, the delete- 

 rious effects were manifested on the system 

 as in the former case.f Experiments of this 

 description appear to have been sufficiently 

 multiplied to establish the fact, that the poison 

 in these cases passed along the vein, and was 

 conveyed in the general mass of the blood. 



The result of these experiments is no doubt 

 very remarkable, and what would scarcely 

 have been anticipated; yet we may remark, 

 that there is one circumstance connected with 

 them, which, in a great measure, invalidates the 

 conclusion that has been supposed to follow so 

 necessarily from them. It may be inferred 

 from the expression made use of, that the 

 poison employed, which was the extract of 

 the upas tree, was inserted by a puncture or 

 incision into the foot of the animal, and would, 

 therefore, in the first instance, be mixed with 

 the blood ; so that the only deduction which we 

 are warranted to draw from the experiment is, 

 that the venous blood, being infected with the 

 poison, had the power of communicating the 

 infection to the system at large.J On this 

 view of the subject we should not regard the 

 above as a case of absorption, but merely as 

 an instance of the power of extraneous sub- 

 stances, under certain circumstances, of uniting 

 with the venous blood and retaining their 

 specific properties. 



In connexion with these experiments of 

 M. Magendie and his associates, we have 

 another series which were performed by MM. 

 Tiedemanri and Gmelin, and which bear di- 

 rectly upon the question of venous absorption. 

 Their object was to ascertain whether there 



* Magendie, Journ. t. i. p. 25 . . 7. 

 t Journ. t. i. p. 23 et seq. ; Elom. t. ii. p. 183 , . 5. 

 J See llullier, ubi supra, p. 150 . . 2 : and Adelon, 

 " Absorption," Diet, de Med. t. i. p. 148. 



