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312 HISTOKY OF DENTAL SUEGBKY

j'pgiiliiting, introdnced what he termed a "crib," designed as an anchorage at-
tacluuent for plates of various kinds. It consisted of a round iridio-phitinum
wire bent to tit and hug both tlie lingual and Iniccal surfaces of the side or
posterior teeth near their necks, with connecting wires passing between or
over tlie occlussal surfaces of these teeth. It was designed, and at first em-
ployed exclusively for retaining purposes, but its use was afterward extended
so as to make it serve as a base for regulating devices constructed solely of
wire and operating itpon the spring principle. In his practice it soon super-
seded the use of vulcanite plates, jackscrews and other jnevioitsly used de-
vices, and became tlie foundation of the system which has since been associated
with liis name. In appearance his crib somewliat resembled the devices
of Delabarre and Schange, although those were used principally for tempo-
rarilv opening the bite. The various ways in which the wire and spring idea
has been carried ottt in the Jackson appliances are almost numberless, but
in principle they consist of the lient wire crib for anchorage, a heavy base wire
extending around the inside of the arch, to wliich the cribs on each side are
attached and the supplementary short wires or finger springs, which exert di-
rect force upon the teeth to be moved and wliich are united to the base wire. In
the gradual development of the appliances the iridio-platinum wire gave wav
to the employment of piano-wire on account of its greater power and lesser
bulk, but this has since been superseded by Gennan silver containing a large
percentage of nickel. Inasmuch as time has proven that the Jackson appli-
ances in their varied forms are capable of producing any of the desired move-
ments in regulation, and serve equally well in the matter of retention, the
following claims made by the originator of the system seem to be justified:
1. Ease of construction and alteration.
2. Firm anchorage.
.3. Occupation of little space in the moutli and hence least interference
with speech and mastication.
1. Cleanliness; the patient being able to remove and insert the appliance.

Dr. Jackson was one of the early advocates of continuous pressure in pre-
ference to intermittent pressure so strongly advocated by Dr. Farrar. Using
the springiness of metals as his sole source of power, Dr. Jackson's methods are
ill strong contrast to those of all other prominent orthodontists, most of whom
avail themselves of a variety of power-producing appliances. In another re-
spect also. Dr. Jackson stands out in contrast with his fellow specialists. While
the question of the relative advantages of removable and non-removahlp appli-