CHAPTER VII. 



ON THE PROPERTIES OF THE LYMPH CONTAINED IN THE LYM- 

 PHATIC VESSELS, AND OF THAT WHICH LUBRICATES THE 

 DIFFERENT CAVITIES OF THE BODY. 



As the fluid contained in the lymphatic vessels resembles 

 water in the circumstances of transparency and want of colour, 

 thence their first discoverers denominated these vessels ductus 

 aquosi, and seem to have concluded that the lymph was nothing 

 but water. 



This opinion some of the succeeding physiologists, particu- 

 larly the learned Boerhaave, rendered more probable, by sup- 

 posing that there were three series of arteries, the sanguiferous, 

 the seriferous, and the lymphatic, and that those lymphatic 

 vessels we are now describing were only veins corresponding 

 to the lymphatic arteries, to restore their lymph to the heart. 

 Thence the lymph seems to have been concluded the thinnest 

 part of our fluids ; in which opinion physiologists were con- 

 firmed by Leeuwenhoeck's theory, that the globules of lymph 

 were smaller than those of the serum, or of the red part of the 

 blood. 



The fluids that moisten the different cavities of the body, 

 viz. that of the peritoneum, pleura, pericardium, &c., being sus- 

 pected to be formed solely from the condensation of that steam 

 which appears on opening an animal just killed, have thence 

 been also considered as mere water by some anatomists and 

 physiologists, who were confirmed in this opinion by observing 

 that in dropsies, where a great quantity of fluid is let out from 

 such cavities, it is commonly a mere water, seldom coagulating 

 either when exposed to the air or to heat. 1 



But, notwithstanding the plausibility of all the arguments 



1 Agreeably to this opinion, these dropsies are said to be occasioned by an in- 

 creased secretion or an impeded absorption, which supposes that the fluids naturally 

 moistening these cavities are the same as those let out from them in dropsical cases. 



