CLASS II. i. 6. 7. OF SENSATION. 145 



3. Pus is diffufible through a diluted vitriolic ncid, though 

 mucus is not ; the fame occurs with water, or a folution of fea 

 fait. 



4. Nitrous acid diflolves both pus and mucus ; water added 

 to the folution of pu produces a precipitate ; and the fluid a- 

 bove becomes clear and green ; while water and the folution of 

 mucus form a dirty coloured fluid. 



" 5. Alkaline lixivium diflolves (though fometimes with dini- 

 jculty) mucus, and generally pus. 



" 6. Water precipitates pus from fuch a folution, but does not 

 jmicus. 



" 7. Where alkaline lixivium does not diflblve pus, it ftill dif- 

 tinguimes it from mucus ; as it then prevents its diiFufion through 

 water. 



" 8. Coagulable lymph is neither foluble in diluted nor con- 

 centrated vitriolic acid. 



" 9. Water produces no change on a folution of ferum in al- 

 kaline lixivium, until after long (landing, and then only a very 

 /light fediment appears. 



" 10. Corrofive fublimate coagulates mucus, but not pus. 



" From the above experiments it appears, that ftrong vitri- 

 olic acid and water, diluted vitriolic acid, and cauftic alkaline 

 lixivium and water, will ferve to diftinguim pus from mucus ; 

 that the vitriolic acid can feparate it from coagulable lymph, and 

 alkaline lixivium from ferum. 



" And hence, when a perfon has any expectorated material, 

 the compofition of which he wifhes to afcertain, let him diflblve it 

 in vitriolic acid, and in cauftic alkaline lixivium ; and then add 

 pure water to both folutions : and if there is a fair precipitation in 

 each, he may be aflured that fome pus is prefent. If in neither a 

 precipitation occurs, it is* a certain teft, that the material is en- 

 tirely mucus. If the material cannot be made to diflblve in al- 

 kaline lixivium by time and trituration, we have alfo reafon to be- 

 lieve that it is pus." Experiments on Pus and Mucus. Cadell. 

 London. 



Dr. Cappe, of York, in his inaugural treatife de Heclica, and 

 Dr. Ryan, of Dublin, in his Eflay on Confumption, have repeat- 

 ed thefe experiments of Mr. Darwin with nearly fimilar refults. 



7. Pbthijis pulmonalis. In pulmonary confumption the fever 

 is generally fuppofed to be the confequence of the ftimulus of 

 abforbed matter circulating in the blood- veflels, and not fimply 

 of its (limulus on their extremities in the furface of the ulcers ; 

 as mentioned in Clafs II. i. 5. and Clafs II. i. 3. 9. The ul- 

 cers are probably fometimes occafioned by the putrid acrimony 

 <rf effufed blood remaining in the air-cells of the lungs after an 



hsemoptoe. 



