xxii INTRODUCTION. 



Dr. Monro, in a letter read before the same Society on the 

 19th of January, 1769, and in a separate publication. 1 A bitter 

 controversy followed. Hewson's answer to Dr. Monro was 

 given in the Appendix to the first and following editions of his 

 * Inquiry into the Properties of the Blood/ and Dr. Monroes 

 rejoinder in the seventh chapter of his large work on the 

 f Structure and Physiology of Fishes/ eleven years after Hewson's 

 death. 



After the supposed discovery by Dr. Hunter or Dr. Monro, 

 that absorption in the animal body is exclusively performed by 

 the lymphatic vessels, the question of the existence of these 

 vessels in birds, reptiles, and fishes appeared of the highest im- 

 portance ; and the supporters of this doctrine of absorption felt 

 the necessity of showing that these animals possess a lymphatic 

 and lacteal system, which was at that time disbelieved by many 

 anatomists; and even by Dr. Monro, as late as 1758. 2 



But the question has now lost much of its interest, because 

 the lymphatic vessels are no longer held to be the exclusive 

 agents of absorption; 3 and the main point contended for by 

 Dr. Monro and Mr. Hewson, to wit, the honour of the first 

 discovery of the lacteal vessels in oviparous vertebrate animals, 

 does not strictly belong to either of the disputants ; for the 

 lacteals of a fish were observed above a century before by 

 Thomas Bartholin, 4 though his description was alloyed with 

 the old error, that they terminate in the liver. It was well 

 remarked by Mr. Abernethy, 5 that all our knowledge of the 

 absorbing vessels has been obtained by fragments, and that our 

 future acquisitions must be made in the same manner. 



But whatever may be thought now of the question of dis- 

 covery, it must be allowed that the lymphatic system of the 



1 ' A State of Facts concerning the first Proposal of performing the Paracentesis 

 of the Thorax, on account of Air effused from the Lungs into the Cavities of the 

 Pleurae ; and concerning the Discovery of the Lymphatic Valvular Absorbent System 

 of Vessels in Oviparous Animals, in Answer to Mr. Hewson ; by Alexander Monro, 

 Physician and Professor of Physic and of Anatomy in the University of Edinburgh.' 

 8vo, Edinb. 1770. 



2 Observations, Anatomical and Physiological, p. 57, 8vo, Edinb. 1758. 



3 See Note LXXXII, page 179. 



4 De Lacteis Thoracicis in Homine Brutisque nuperrime Observatis, Historia Ana- 

 tomica, p. 70, 12mo, Lond. 1652. 



5 Philosophical Transactions, 1796, p. 33. 



