LYMPHATIC SYSTEM. 165 



and degree of the inflammation, the pus may vary from the 

 bland, viscid, and inodorous nature, to that of the most thin and 

 fetid sanies found in phagedenic and cancerous ulcers. And if 

 pus in these cases is produced merely by a secretion (see Note 

 LXXII), so likewise, it would seem probable, that even in ab- 

 scesses, where there is a loss of substance, it is not the melting 

 down of the solids that gives rise to the pus, but the pus 

 being secreted into the cellular membrane, from its pressure, and 

 from other causes, deadens the solids and then dissolves them ; 

 which is confirmed by observing that even a piece of fresh 

 meat, if put into an ulcer and covered up, is soon destroyed or 

 melted down by the pus, which is thereby rendered more 

 fetid (LXXV). And this opinion that pus is made by a secre- 

 tion is strengthened by observing that in its pure state it is 

 full of globules ; in which circumstance it agrees with milk, 

 which is produced by a secretion, and not by a fermentation. 1 



Upon the whole, then, it appears that the lymph contained 

 in the lymphatic vessels, and the fluids which moisten the dif- 

 ferent cavities of the body, as the pleura, peritoneum, &c., 

 instead of being a mere water in healthy animals, are coagu- 

 lable fluids (see Notes LXVIII and LXIX), approaching to the 

 nature of the coagulable lymph of the blood, of which pro- 

 bably they are a species, or are composed of a mixture of 

 that lymph with water, that the proportions of that mixture 

 vary from the dropsical habit, where the coagulable lymph is 

 in a small, and . the water in a great proportion, up to the 

 rheumatic or inflammatory habit, where the lymph abounds, 

 and the water is in less proportion ; and that in some cases 

 the lymph, in passing through inflamed vessels, is even con-, 

 verted into pus. 



1 See Professor Morgan's ingenious Dissertation, De Puopoiesi. 



(LXXV.) According to the experiments of Sir E. Home a pus has no 

 particular effect in dissolving muscular fibre, which agrees with the 

 result of several trials that I made. The effect on the muscular fibre 

 mentioned in the text, probably arose from putrefaction, favoured by 

 the heat of the ulcer. Pus itself is less prone to putrefaction than 

 blood and most animal juices. 



* On the Properties of Pus, pp. 32-36, 4to, Lond. 1788. 



