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OTHER BRANCHES OF MEDICAL SCIENCE. 379
Ophthalmology made a great stride at this time, in laying
aside the error, that cataract results from an extra-ocular
humour which is deposited in the form of an opaque pellicle
before the lens, and by adopting the correct view that it
consists of a disease of the lens itself. This discovery
received a splendid confirmation in the method of extraction
by which DAVIEL in 1746 performed the first operation
for removal of the lens. Extraction from this time
forth maintained an established position in ophthalmic
surgery along with the couching operation. The formation
of an artificial pupil constituted a further step in advance;
this was advocated by WOOLHOUSE and first performed in
1728 by CHESELDEN. The procedure consisted of an
incision made in the iris ; the elder WENTZEL modified
this by excising a portion of the iris—performing an iridectomy
in fact.
To this period midwifery owes the beneficent discovery
of the forceps. Long led up to by the instruments which
obstetricians made use of for the extraction of dead
foetuses, they appeared upon the scene finally in the 17th
century and assumed a form calculated to adapt them to
their peculiar ends. The CHAMBERLENS in difficult labours
made use of appliances consisting of levers, or blades of
steel covered with leather. This invention remained a
business-secret until JEAN PALFYN made it public after
introducing many improvements.* It was then further
perfected by DUSE, who introduced the crossing of the two
blades, by the younger GREGOIRE who had them fenestrated
and united by a locking apparatus, and above all by
LEVRET who changed the straight form of the blades into a
curved one, arranged for the locking by means of a moveable
peg, and laid down a statement of the indications
which justified the use of the forceps. To avoid the
dangers of Csesarean section—an operation but rarely performed—a
division through the symphysis pubis was
* J. H. AVELING: The Chamberlens and the midwifery forceps, London
1882.—A. GOFFIN: Jean Palfyn, Bruxelles 1887.