GLASS II. 1. 6. 7. OF SENSATION,] 245 



" 3. Pus is diffusible through a diluted vitriolic acid, though 

 mucus is not; the same occurs with water, or a solution of sea 

 salt 



"4. Nitrous acid dissolves both pus and mucus; water added 

 to the solution of pus produces a precipitate; and the fluid above 

 becomes clear and green; while water and the solution of mucus 

 form a dirty coloured fluid. 



" 5. Alkaline lixivium dissolves (though sometimes with diffi- 

 culty) mucus, and generally pus. 



" 6. Water precipitates pus from such a solution, but does not 

 mucus. 



" 7. Where alkaline lixivium does not dissolve pus, it still dis- 

 tinguishes it from mucus; as it then prevents its diffusion through 

 water. 



u 8. Coagulable lymph is neither soluble in diluted nor con- 

 centrated vitrolic acid. 



" 9. Water produces no change on a solution of serum in al- 

 kaline lixivium, until after long standing, and then only a very 

 slight sediment appears. 



" 10. Corrosive sublimate coagulates mucus, but not pus. 



lc From the above experiments it appears, that strong vitri- 

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

 lixivium and water, will serve to distinguish pus from mucus; 

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

 alkaline lixivium from serum. 



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

 the composition of which he wishes to ascertain, let him dissolve 

 it in vitriolic acid, and in caustic alkaline lixivium; and then 

 add pure water to both solutions, and if there is a fair precipi- 

 tation in each, he may be assured that some pus is present. If 

 in neither a precipitation occurs, it is a certain test, that the 

 material is entirely mucus. If the material cannot be made to 

 dissolve in alkaline lixivium by time and trituration, we have 

 also reason to believe that it is pus." Experiments on Pus and 

 Mucus. Cadell. London. 



Dr. Cappe, of York, in his inaugural treatise de Hectica, and 

 Dr. Ryan, of Dublin, in his Essay on Consumption, have repeat- 

 ed these experiments of Mr. Darwin with nearly similar results. 



7. Phthisis pulmonalis. In pulmonary consumption the fever 

 is generally supposed to be the consequence of the stimulus of 

 absorbed matter circulating in the blood-vessels, and not simply 

 of its stimulus on their extremities in the surface of the ulcers; 

 as mentioned in Class II. 1. 5. and Class II. 1. 3. 9. The ul- 

 cers are probably sometimes occasioned by the putrid acrimony 

 of effused blood remaining in the air-cells of the lungs after an 



