e nutrition and strong recuperative power, it may
exist for years without doing permanent damage. But joined to causes of
the first type, lowered nutritive activity, it causes rapid and
permanent loss of sight. The third group are cases associated with
glaucoma only as causes. In eyes with low nutritive power, or subject to
exacerbations of increased intra-ocular pressure, uveal inflammations
may prove disastrous. The fourth type shows the results of the
combination of the causes of the other types; with the elements of acute
or slow malignancy added--the impaired circulation and lowered oxidation
producing some degree of edema of the tissues that insures a fatal
result.

This is no complete presentation of my subject, but a selection of facts
bearing on the etiology, to serve as a foundation for the discussion of
those practical aspects of glaucoma which are to claim your attention
through the papers and remarks of subsequent speakers.

Dr. Edward Jackson's Paper on Etiology and Classification of Glaucoma

Discussion,

FRANCIS LANE, M.D.

Chicago.

Not one of the theories thus far propounded to explain the essential
cause of increased intra-ocular tension is satisfactory. Our present day
knowledge apparently ceases with a more or less incomplete understanding
of the mere circumstance under which increase of tension in general
depends.

The question of the source of the normal intra-ocular pressure must
first be solved before any discussion of a pathological increase can be
engaged in. This question primarily hinges on whether the corneo-sclera
is to be regarded as an unelastic capsule with a fixed volume, or as a
yielding envelope with an ever changing capacity.

This brings us at once to the consideration of that theory which
probably has held our attention for the longest period of time, _i. e._,
the volumetric theory. According to it, the normal intra-ocular tension
depends on the volume of fluids within the eyeball. Any variation in the
quantity of the contents gives rise to a change in the pressure,
therefore, the globe has been regarded as "an elastic capsule, whose
capacity, form, and internal pressure depend on the balance struck
between a constant inflow, or formation of aqueous, and a proportionate
outflow or resorption." (Henderson.)

Hill has satisfactorily demonstrated that, under physiological
conditions, the hydrostatic pressure within the eye and the skull is
identical; it rises and