Dr. Pearson 's Observations 
006 
sulphate of soda, &c. being mixed in due quantity with pus of 
the kinds under examination produce viscidity, like ropy ex- 
pectorated matter, thickening like jelly, and less opacity. 
These changes have, in the case of muriate of ammonia, been 
called coagulation by Mr. Hunter ; but by agitation in cold 
water the matters are diffused, and on standing, the pus is 
precipitated in its original state. I call these effects of the 
neutral salts inspissation, seemingly occasioned by their at- 
tracting water from the pus; for no such change is produced 
if either the purulent matter, or solution of salts be diluted ; 
nor is it produced if the pus be previously coagulated by 
cploric: also the inspissated pus is coagulable by caloric as 
usual. No such inspissation is produced by these salts in 
mucous sputum, nor in muco-purulent sputum, so that un- 
doubtedly it is a criterion as discovered by Mr. Hunter in the 
case of muriate of ammonia, and with other neutral salts, 
as now manifested. 
4. 1 endeavoured to find some easy tests for distinguishing 
pus from mucus ; but I did not succeed with the tanning 
principle ; gallic acid ; super sulphate of alumina ; nitrate of 
silver, and other metallic salts ; and as already said, various 
acids. They all produced precipitation of these animal mat- 
ters, but not with observable characteristic differences. 
5. To observe the state in which the matter of pus is 
secreted, I procured the assistance of Mr. Maynard, the 
present house-surgeon of St. George's hospital, and Mr. 
George Ewbank, who had been on many occasions essen- 
tially serviceable in my inquiries. Square pieces of gold 
beater's skin were applied to various sore legs after carefully 
removing the matter already secreted. In five to ten minutes 
