46 Professor Burnett's 
physician; whilst others, in other persons, or even in the 
same person at other times, not the most consummate skill can 
cure. Of this, the records of legitimate practice would afford 
us abundant illustrations; but the empirical artifices of the 
present day form still more familiar examples: to these I shall 
not particularly allude: some will Jong be notorious beacons. 
From these sources of error, many useless, many nauseous, 
and not a few noxious, agents have, from time to time, been 
introduced, several of which have enjoyed an ill-earned fame; 
while some really efficient medicines have as undeservedly 
fallen into disrepute. Hence, likewise, can we account for 
many of those superstitious rites, anciently so mixed up with 
medicine as to have been esteemed an essential part thereof. 
Few persons will take the trouble of distinguishing the post 
from the propter; and, even to those who would, the power 
is oft-times wanting. A mind, patient in observation, and 
well disciplined to distinguish truth from error, does not com- 
monly coexist with that instinct (shall I call it almost blind 
instinct,) for generalization, by which theories are planned, 
and systems raised. Allow an example to illustrate this ab- 
stract proposition. 
Achilles, writes the poet, escaped unhurt, though long 
exposed to all a warrior’s danger, (and so did others of the 
Grecian force, and so do many others in every hostile meet- 
ing;) Achilles at last was slain by an arrow which transfixed 
his heel, (and so have many others fallen by wounds in some 
especial parts, whether in the head, the hand, the heel, for 
weapons to each victim are not omnipresent;) but Achilles 
had been bathed by Thetis, (and so by most parents have 
their sons been washed ;) yet it is fabled that the heel by 
which his mother held him was the only part unwetted; that 
heel, itis said, was pierced; and hence arose the fame of the 
antivulneriferous waters of the Styx. ‘‘ Post ergo PROPTER 
balneum salus.” 
Again, in times of general sickness, the Romans, with 
solemnity, elected a Dictator, for the especial purpose (and 
that alone) of driving a nail into the temple of Jupiter, and 
when afterwards the pestilence decreased, post ergo propter 
malleum salus. 
Just as, at the present time, in countries where the plague 
prevails, an angel is believed to cast a drop of water on the 
earth, on the festival of St. John, after which day the plague 
is stayed, and to which the restoration of salubrity is attri- 
buted, rather than to the actual cause, viz. the great increase 
of heat that then ensues, and which is incompatible with its 
duration. 
