278 Description of a Totally Reflecting Prism. 



the tube of the apparatus very convenient for the illumination 

 of the auditory passage." Op. cit. p. 92. 



This large and incommodious lantern is liable to the general 

 objection applicable to all such means of illuminating the 

 cavity of the ear, that any direct light, even of the sun itself, 

 is unavoidably liable to be intercepted by the head of the 

 observer in so narrow a field ; and if a lamp and lens be placed 

 between the eye and the object viewed, not only does the 

 dazzling artificial medium alter the characteristic appearance 

 of disease, but such apparatus, in order to guide any surgical 

 procedure, must be kept strictly in such a position as neces- 

 sarily to interfere with any convenient manipulation in the 

 removal of foreign bodies from the ear, the puncture of the 

 membrane of the tympanum, the application of caustic, or 

 any other operation. The method of illuminating diseased 

 parts by the prism is not liable to these objections. The 

 cavity of the ear and other deeper seated parts may be inspect- 

 ed with the satisfaction only short of sunlight view, by means 

 of a common gas jet or other light, and with little less facility 

 than the tongue; while by the position of the prism in the 

 apparatus, it presents no obstruction to the procedure of the 

 surgeon, — a circumstance which commends it to the operator 

 in diseases of the rectum and uterus, where the application of 

 ligatures, cauteries, &;c., render any increased facilities pecu- 

 liarly desirable. 



To those who are at all acquainted with the progress of the 

 medical art in our own day, it is well known that this has 

 been chiefly owing to the more exact investigation and the 

 more extended knowledge possessed of the alterations which 

 take place in parts affected with disease, and the minute 

 detail of physical appearances which medical authors employ 

 to describe these changes, is well calculated to convey an idea 

 of the great and just importance attached to them. In pro- 

 portion as we attain to the means of recognizing with preci- 

 sion the actual state of disease in the interior parts of the 

 body, will its successful treatment be insured ; and if, by the 

 method here proposed, we can in any case confirm the doubt- 

 ful testimony of touch, by the farther evidence of sight, which 

 before was wanting, it is obvious that the full force of medical 



