223 OF GLANDS. Sect. XXVI. 2. 3, 



that in their inflamed ftate they have the greateft fenfibility to 

 pain, as in the pleurify and paronychia. 



3. On all thefe membranes a mucilaginous or aqueous fluid is 

 fecreted, which moiftens and lubricates their furfaces, as was 

 explained in Section XXIII. 2. Some have doubted, whether 

 this mucus is feparated from the blood by an appropriated fet of 

 glands, or exudes through the membranes, or is an abrafion or 

 cleftruclion of the furface of the membrane itfelf, which is con- 

 tinually repaired on the other fide of it, but the great analogy 

 between the capillary vefTeis, and the other glands, countenances 

 the former opinion $ and evinces, that thefe capillaries are the 

 glands, that fecrete it ; to which we muft add, that the blood in 

 pafling thefe capillary vefTeis undergoes a change in its colour 

 from florid to purple, and gives out a quantity of heat ; from 

 whence, as in other glands, we muft conclude that fomething 

 5s fecreted from it. 



III. The feat of rheumatifm is in the membranes, or upon 

 them *, but there are three very diftincl: difeafes, which com- 

 monly are confounded under this name. Firft, when a mem- 

 brane becomes afiTecled with torpor or inactivity of the vefTeis 

 which compofe it, pain and coldnefs fucceed, as in the hemicra- 

 jiia, and other head-achs, which are generally termed nervous 

 jheumatifm ; they exift whether the part be at reft or in motion, 

 and are generally attended with other marks of debility. 



Another rheumatjfm is faid to exift, when inflammation and 

 fwelling, as well as pain, afrecT: fome of the membranes of the 

 joints, as of the ancles, wrifts, knees, elbows, and fometimes of 

 the ribs. This is accompanied with fever, is analogous to pleu- 

 xify and other inflammations, and is termed the acute rheu- 

 jnatifm. 



A third difeafe is called chronic rheumatifm, which is diftin- 

 guiihed from that firft mentioned, as in this the pain only af- 

 .tccts the patient during the motion of the part, and from the 

 fecond kind of rheumatifm above defcribed, as it is not attend- 

 ed with quick pulfe or inflammation. It is generally believed 

 to fucceed the acute rheumatifm of the fame part, and that fomc 

 coagulable lymph, or cretaceous, or calculous material, has 

 been left on the membrane ; which gives pain, when the muf- 

 cles move over it, as fome extraneous body would do, which was 

 too infoluble to be abforbed. Hence there is an analogy be- 

 tween this chronic rheumatifm and the difeafes which produce 

 gravel or gout-ftones ; and it may perhaps receive relief from, 

 the fame remedies, fuch as aerated fal foda. 



SECT. 



