[BowMax] FUNDAMENTAL PROCESSES IN HISTORICAL SCIENCE 143 
being correctly prepared and labelled unless there be manifest indica- 
tion of the contrary by reason of an unusual appearance or odor in the 
drug or unexpected effects from its use. He has indeed the expert 
knowledge requisite to test chemically every drug supplied, but the 
demands of his calling are such that he cannot ordinarily make such 
tests, and since for that reason he is not in a position to judge of the 
matter for himself, he as a reasonable man accepts the drugs supplied 
as being correctly prepared and labelled save where, as above stated, 
there is manifest ground to suspect or to believe the contrary. And 
thus also in actual practice the patient in turn as a reasonable man, 
accepts and uses the prescribed medicine, when the prescription has 
been filled by the druggist, as being correctly compounded; for the 
ordinary patient has not the expert knowledge requisite to judge of 
the correctness of the druggist’s work other than by observing the 
effect of the medicine, when so used, on himself: and even though 
the patient had such expert knowledge, he would think it unreasonable 
to put himself to the inconvenience of making a chemical test unless 
there were manifest grounds for suspecting an error by reason of an 
unusual appearance or odor in the remedy or unexpected effects from 
its use. 
In the various forms of professional and other service, some of an 
intricate and others of a simple nature, the same principle may be 
observed in continual and effective operation. The processes, e.g., of 
land-surveying, conveyancing and book-keeping, are such that if the 
surveyor, conveyancer or book-keeper does not deviate from the re- 
quirements of these processes, the results obtained will be necessarily 
correct. Any person having need of such service employs for the 
purpose individuals who, either by public licence or by their calling in 
the community, are accredited as operators of the processes involved ; 
and any such employing parties, if they have not the professional skill, 
knowledge or time necessary for checking the work performed, are 
required as reasonable men to accept the work done by the parties 
employed as correct unless the contrary be proven; and in actual fact, 


! In this connection it should be noted that the student of chemistry acts on 
the same principle in prosecuting his studies or researches in the laboratory. He 
has the scientific knowledge to test chemically every reagent supplied to him in order 
to ascertain whether it actually is what by its label it purports to be. He could not, 
however, habitually make such confirmatory tests without hindering unduly his 
proper activity; and unless there are manifest grounds for suspecting the correctness 
of the label by reason of an unusual appearance or odour in the reagent or unexpected 
results from its use in his work, he accepts the reagent supplied to him as being what 
by the label it purports to be: and from that point and on that basis he prosecutes 
his chemical studies and researches. 
