LYMPHATIC SYSTEM. 121 



the thoracic duct, it was natural for anatomists to suspect, 

 that as the lacteals opened into the intestines to absorb, the 

 lymphatic vessels (which are branches of the same system) 

 might possibly do the same office with respect" to other parts 

 of the body ; and accordingly Dr. Glisson, who wrote in 1654 

 (that is, the very year after Bartholin published on the lym- 

 phatic vessels), supposes these vessels arose from cavities, and 

 that their use was to absorb ; and Frederic Hoffman has very 

 explicitly laid down the doctrine of the lymphatic vessels being 

 a system of absorbents. 1 But anatomists in general have been 

 of a contrary opinion ; for, from experiments, particularly such 

 as were made by injections, they have been persuaded that the 

 lymphatic vessels did not arise from cavities, and did not ab- 

 sorb, but merely were continued from small arteries. The 

 doctrine therefore that the lymphatics, like the lacteals, were 

 absorbents, as had been suggested by Glisson and by Hoffman, 

 has been revived by Dr. Hunter and Dr. Monro, who have 

 controverted the experiments of their predecessors in anatomy, 

 and have endeavoured to prove that the lymphatic vessels are 

 not continued from arteries, but are absorbents. 



To this doctrine, however, many and strong objections have 

 been started, particularly by the learned M. de Haller, 2 and it 

 has been found, that before the .doctrine of the lymphatics 

 being a system of absorbents can be established on a solid 

 foundation, it must first be determined, whether other animals, 

 besides man and quadrupeds, have or have not this system. I 

 have been so fortunate as to prove the affirmative of this ques- 

 tion, by discovering the lymphatic system in birds, fish, and 

 amphibious animals, 3 and in consequence of these discoveries I 

 have also arrived at the knowledge of considerable varieties in 

 the composition of those vessels through the various classes of 

 animals; by comparing this knowledge with some facts that 

 I have lately observed concerning the blood, I have thence 

 been led to ascertain the use of the lymphatic glands, the thy- 

 mus, and the spleen ; which have so long been considered as 

 the opprobria of anatomists. 



These last observations I propose making the subject of a 



1 See further on, chapter x. 2 Elem. Phys. lib. xxiv, sect. 2, 3. 



3 Accounts of which have already been published in the Phil. Transactions, vols. 

 Iviii, lix. 



