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gen gas is necessary to the continuance of living ac- 
tion ; that this gas disappears during the exercise of 
the respiratory function ; and that a portion of car- 
bonic acid is, at the same time, produced: but the 
real nature of these changes in the air, the extent to 
which they proceed, and the mode in which they are 
accomplished, cannot be learned from the labours of 
Spallanzani. With all his zeal for experiment, and 
all his ingenuity, this philosopher, indeed, seems not 
clearly to have apprehended the true nature and ob- 
jects of experimental science. The mere multiplica- 
tion of experiments serves only to multiply error, 
unless the mind exercise a severe judgment over the 
observations of sknse, and, by separating what is ne- 
cessary from what is accidental, endeavour to trace 
the order and succession of events, and to ascertain 
the mode and degree in which they are finally ac- 
complished. " Inductio, enim, quse procedit per 
enumerationem simplicem," says the great Father of 
experimental science, " res puerilis est, et precario 
concludit; et periculo exponitur ab instantia contradic- 
toria, et plerumque secunduin pauciora quam par est, 
et ex his tantummodo quas presto sunt, pronunciat. 
At induct io, quae ad inventionem et demonstrationem 
scientiarum et artium erit utilis, naturam separare 
debet, per rejectiones et exclusiones debitas ; ac 
deinde post negativas tot quot sufficiunt, super affir- 
mativas concludere V Even when this separation 
and rejection shall be made, the facts thus acquired 
Nov. Oniun. lib. i. 
