Dr. Pearson's Observations 
314 
pus and mucus. Hence the parties are not able to perceive 
that in this kind of sputum, exist many of the properties of 
pus, and also of mucus. I have described it in my former paper 
on expectorated matter, Phil. Trans. 1809.. P. II. p. 317, under 
the denomination of opaque ropy matter , the third kind. I feel 
no degradation in finding it necessary to confess, that a better 
acquaintance with the properties of pus, has taught me that I 
was in an error, in considering this kind of expectorated 
* matter to differ from other sorts, merely in the proportion, 
and not in the kinds of constituent parts. It now appears, that 
the sputum in question possesses such properties as might be 
predicted to exist, from the known properties of pus and 
mucus separately, in case these two substances should be in- 
timately commixed. Accordingly, the opacity ; the straw 
colour ; the greater density than mucus ; the great globu- 
larity under the microscope; the greater proportion of residue 
on evaporation to dryness, than from mucus ; the milky liquid 
on heating this matter ; the milkiness on agitation in cold 
water ; are properties of pus. But the great viscidity, yet not 
increased by neutral salts ; the less opacity than pus ; the less 
globularity than pus ; the smaller proportion of exsiccated re- 
sidue than from pus ; the moisture, or greater moisture on the 
exposure of the brittle residue to air, than from that of pus ; the 
more difficult diffusibility through cold water, and less degree 
of milkiness than from pus : the great proportion of leafy or 
fibrous masses on agitation in a very large quantity of cold 
water ; the speedy putrescency ; are properties of mucus. 
The mode of coagulation by caloric at 160° and upwards, is 
such as might be expected from the commixture, viz. in large 
jmasses of curd in a milky liquid, instead of into one uniform 
