426 Original Articles. , [July, 
them and those which result from altered and abnormal conditions of 
the tissues ; and after he has arrived at this knowledge he must further 
learn by frequent examination and careful reasoning, to determine not 
only in which particular structure the change may be, but the exact 
nature of the change and the stage of it, whether it indicates an 
altered condition of a temporary unimportant character, or a morbid 
state of a more permanent or even irremediable kind; whether the 
disease be in an early stage, with commencing mischief, or at a period 
of decline, when any change which is likely to result from it has 
already been accomplished. He must further know whether any treat- 
ment (and if any, of what nature) is likely to be beneficial ; or whether 
the change involves such organic alteration in the structure of the part, 
that no remedies can benefit: even further information may be obtained 
if this latter condition be established, for we learn whether the disease 
be such as may be limited to the eye or may extend to the whole sys- 
tem, ultimately destroying not only the organ itself, but the life of the 
patient. It is upon the answers given to these, and similar important. 
questions, that the knowledge revealed by the ophthalmoscope is de- 
stined to be of the utmost value. We say advisedly “ destined to be,” for 
though fully prepared to recognize the great steps in advance, which 
the diligence of comparatively few observers has secured, and to 
acknowledge that many of the more clearly marked diseases are 
already readily diagnosed, it must be confessed that much still 
remains to be done; there is still much to be learnt, and something 
to be unlearnt. For ardent minds will dogmatize on insufficient. 
data, and inexperience is apt to overlook difficulties which stand in 
the way of those who know more; while ignorance will not unfre- 
quently hazard a rash assertion rather than confess to a want of ex- 
perience in the use of an instrument with which a patient, having 
heard something wonderful about it, expects, as a matter of course, 
that the party he consults should be perfectly familiar. We could cite 
examples of strange assertions and crude speculations which have been 
made after gravely peeping through an ophthalmoscope. This, how- 
ever, is no valid argument against the value of the discovery itself. 
The difficulty of acquiring any technical knowledge, sufficiently pre- 
cise to be valuable, is often great ; far more so than many people sup- 
pose. No greater advance in the means of detecting and distinguishing 
diseases of the chest has ever been made than through the invention of 
the stethoscope. Now what this simple instrument is to the chest, the 
ophthalmoscope is and will be to the eye. It has required nearly fifty 
years of diligent observation, and the labour of thousands of learned 
men over almost the whole world, to define the revelations of the 
stethoscope as now understood by the initiated, and still there are 
multitudes who make a show of using it, but do not understand its 
teachings. So it is, and probably long will be, with the ophthalmo- 
scope. 
a aches which are not now understood, will ere long have 
their true significance shown to those who will take the trouble to learn ; 
and errors which are now committed will be avoided, while accumu- 
lated experience will clearly indicate the value of that which is now ob- 
