cian of Modena, succeeded in
constructing a reflecting microscope which was said to be superior to
any compound microscope of the time, though the events of the ensuing
years were destined to rob it of all but historical value. For there
were others, fortunately, who did not despair of the possibilities of
the refracting microscope, and their efforts were destined before
long to be crowned with a degree of success not even dreamed of by any
preceding generation.

The man to whom chief credit is due for directing those final steps
that made the compound microscope a practical implement instead of a
scientific toy was the English amateur optician Joseph Jackson Lister.
Combining mathematical knowledge with mechanical ingenuity, and having
the practical aid of the celebrated optician Tulley, he devised formulae
for the combination of lenses of crown glass with others of flint
glass, so adjusted that the refractive errors of one were corrected
or compensated by the other, with the result of producing lenses of
hitherto unequalled powers of definition; lenses capable of showing an
image highly magnified, yet relatively free from those distortions
and fringes of color that had heretofore been so disastrous to true
interpretation of magnified structures.

Lister had begun his studies of the lens in 1824, but it was not until
1830 that he contributed to the Royal Society the famous paper detailing
his theories and experiments. Soon after this various continental
opticians who had long been working along similar lines took the matter
up, and their expositions, in particular that of Amici, introduced
the improved compound microscope to the attention of microscopists
everywhere. And it required but the most casual trial to convince the
experienced observers that a new implement of scientific research had
been placed in their hands which carried them a long step nearer
the observation of the intimate physical processes which lie at the
foundation of vital phenomena. For the physiologist this perfection of
the compound microscope had the same significance that the, discovery
of America had for the fifteenth-century geographers--it promised a
veritable world of utterly novel revelations. Nor was the fulfilment of
that promise long delayed.

Indeed, so numerous and so important were the discoveries now made in
the realm of minute anatomy that the rise of histology to the rank of an
independent science may be said to date from this