$ 1 ° 
Dr. Pearson's Observations 
those of the blood altered by secretion may be determined 
hereafter. It is a collateral proof of this inference that very 
thick pus affords one sixth to one seventh of exsiccated brittle 
residue, which, as I have found, is nearly the same proportion 
afforded on the exsiccation of the huffy coat of inflamed blood ; 
while very thin pus affords on exsiccation one eighth to one 
eleventh of brittle residue, which is the proportion to be ex- 
pected from a mixture of serum of blood and self-coagulated 
lymph, as I have ascertained. 
10. That the constant impregnating saline and earthy 
ingredients of pus, are dissolved in the serous fluid, and are 
all separable along with the serum, by ablutions with water, 
from the opaque oxide (i), except a portion of the phosphate 
of lime. These impregnations are the same as those of 
serum of blood, and of expectorated mucous matter, viz. 
muriate of soda ; potash neutralized by animal matter or a 
destructible acid : phosphate of lime; ammonia neutralized pro- 
bably by phosphoric acid ; with a sulphate and traces of some 
other matters mentioned in my former paper. The proportion 
of these impregnating substances is as the proportion of limpid 
or serous coagulable fluid, and of course inversely as the 
proportion of the opaque oxide of pus ; but it varies in diffe- 
rent cases in given proportions of this oxide, and the limpid 
fluid. In general, if not always, a given quantity of pus contains 
a smaller proportion of saline matters than an equal given 
quantity of expectorated mucous matter, but a given quantity 
of the limpid coagulable fluid contains a greater proportion of 
saline matters than an equal given quantity of serum of blood. 
Hence the thicker the pus the less irritation to the sore which 
secretes it, and commonly the less the inflammatory or other 
