Dr. Pearson’s Observations 
3.12 
itself, according to the different conditions of the animal 
ceconomy. 
According to the above inferences, I trust, a distinct and 
definite notion of the substance to be considered as pus is 
exhibited ; and I do not comment on the different results of 
experiments and conclusions of other writers, because future 
observers only can determine the truth. What is and what 
is not pus will now readily be ascertained by a few easy ex- 
periments ; by the obvious properties ; and by the considera- 
tion of the source of the matter in question : provided, however, 
that it be unmixed with certain other matters by which dis- 
guise is produced. As already observed it is in pulmonic 
diseases that the ambiguity occurs:; and physicians lay very 
considerable stress upon the nature of expectorated matter in 
their practice and reasoning ; I shall therefore endeavour to 
elucidate the subject by remarks on the puriform matter 
expectorated in different cases. 
1. An abscess occasioned by acute inflammation not only 
of a pleurisy, and peripneumony, but of other diseases which 
have not the symptoms of any one which has received a de- 
signation. Here there ought to be no doubt ; for the matter 
which is coughed up suddenly and abundantly on the bursting 
of the abscess is evidently pus with little mucus. Such matter 
consists of the essential ingredients of pus, (Sect. VIL 1,) with 
generally the adventitious substances, (Sect. VII. 2, 3, 4.) viz . 
coagulated lymph, membranous or fibrous parts, and a small 
proportion of the red part of bloods 
2. Purulent expectoration from the rupture of abscesses, or 
vomicae of suppurated tubercles. In such cases there has been 
a chronical cough with viscid sputum, commonly in persons off 
