[FIG. 5.--Cross section of full-lumen esophagoscope for the use of
largest bourgies. The canals for the light carrier and for drainage
are so constructed that they do not encroach upon the lumen of the
tube.]

[25] The special sized esophagoscopes most often useful are the 8 mm.
X 30 cm., the 8 mm. X 45 cm., and the 5 mm. X 45 cm. These are made
with the drainage canal in various positions.

For operations on the upper end of the esophagus, and particularly for
foreign body work, the esophageal speculum shown at A and B, in Fig.
4, is of the greatest service. With it, the anterior wall of the
post-cricoidal pharynx is lifted forward, and the upper esophageal
orifice exposed. It can then be inserted deeper, and the upper third
of the esophagus can be explored. Two sizes are made, the adult's and
the child's size. These instruments serve, very efficiently as
pleuroscopes. They are made with and without drainage canals, the
latter being the more useful form.

[FIG. 6.--Window-plug with glass cap interchangeable with a cap having
a rubber diaphragm with a perforation so that forceps may be used
without allowing air to escape. Valves on the canals (E, F, Fig. 3)
are preferable.]

_Gastroscopes_.--The gastroscope is of the same construction as the
esophagoscope, with the exception that it is made longer, in order to
reach all parts of the stomach. In ordinary cases, the regular
esophagoscopes for adults and children respectively will afford a good
view of the stomach, but there are cases which require longer tubes,
and for these a gastroscope 10 mm. X 70 cm. is made, and also one 10
mm. X 80 cm., though the latter has never been needed but once.

[26] _Pleuroscopes_.--As mentioned above the anterior commissure
laryngoscope and the esophageal specula make very efficient
pleuroscopes; but three different forms of pleuroscopes have been
devised by the author for pleuroscopy. The retrograde esophagoscope
serves very well for work through small fistulae.

_Measuring Rule_ (Fig. 7).--It is customary to locate esophageal
lesions by denoting their distance from the incisor teeth. This is
readily done by measuring the distance from the proximal end of the
esophagoscope to the upper incisor teeth, or in their absence, to the
upper alveolar process, and subtracting this measurement from the
known length of the tube. Thus, if an esophagoscope 45 cm. long be
introduced and we find that the distance from the incisor teeth to the
oc