274 Descnption of a Totally 'Reflecting Prism. 



more serious forms even endangering life itself, will be con- 

 ceived, when it is mentioned that Valsalva, one of the most 

 eminent anatomists of the last century, devoted sixteen years 

 of a laborious life to their investigation, and to the composition 

 of his treatise on the subject. His biographer, Morgagni, men- 

 tions that he performed an incredible number of dissections in 

 this research. The great proportion of the diseases of this 

 organ, and those of the most remediable kind, have their origin 

 in the external auditory canal, and the tympanum at its termi- 

 nation — ^the vascular texture and the situation of those parts 

 exposing them to the first attacks of disease, and, whence, in 

 its unchecked progress, it is propagated to the complicated in- 

 terior structures, to the bones and the brain. 



The external auditory passage exceeds an inch in length, is 

 curved in its course, and is commonly so beset with hairs as to 

 prevent the view of its inward track and termination ; but by 

 the aid of a straight canula, or the common speculum^ these 

 obstacles to observation are readily obviated ; sufficient light, 

 however, to illuminate the passage, still remains the one desi- 

 deratum, without which, to exhibit the actual condition of the 

 membrane of the tympanum, the surgeon cannot pronounce as 

 to the importance or curability of disease, nor resort, with con- 

 fidence of its safety from danger, even to the popular remedy 

 of the syringe. The instrument submitted to the Society, and 

 represented in the Woodcut, is constructed upon the prin- 

 ciple of illumination derived from prismatic reflection. It con- 

 sists of separate portions : a straight handle, a a, five inches in 

 length, terminating in a ring, 6, of half an inch internal dia- 

 meter, the ring grooved in its interior as a screw. To this 

 screw are adapted four canulae or straight tubes, c, of one, 

 two, three, and four lines calibre, and another, d, of a funnel or 

 tapering shape, applicable to the dimensions of the auditory 

 canal at different ages and under different degrees of constric- 

 tion resulting from disease ; the wider mouthed canula is in- 

 tended to be employed for preliminary exploration and removal 

 of any accumulated cerumen obstructing the passage of the 

 light, also for affording a proper field for the passage of instru- 

 ments and other topical manipulation. The canulae are an inch 

 and a quarter in length, and terminate in blunted edges, to 



