280 Description of a Totally Beflecting Prism. 



carried in that particular situation. Those cases of highly- 

 seated stricture which occur at the farther extremity of the 

 straight bowel, and so are removed beyond touch, and all 

 satisfactory management, may, by the method which 1 have 

 proposed, be brought fully under examination, and have the 

 treatment adapted with the same accuracy as in the more 

 superficial affections. 



It is probable that an erroneous idea of the expense of the 

 instruments required for this method of investigation may 

 deter many from making trial of them ; but it will serve to 

 remove this mistake if I shall mention that my experiments 

 were mostly made with the materials within reach of all, such 

 as tubes of block-tin, of bone, aud of rosewood. At the 

 same time, more expensive materials, as silver gilt, silver plate, 

 or German silver, are the most appropriate, and such as I 

 would recommend. The quality and finish of the glass em- 

 ployed admits of lass latitude of choice, — the second or in- 

 terior prism especially must possess that highly-finished sur- 

 face which Messrs Adie & Son, opticians, of this city, are so 

 competent to supply. 



I shall now, as briefly as possible, explain the parts which 

 compose another of the forms of the Prismatic Speculum, of 

 which a plate is appended (Plate IV.) to this paper. Any dif- 

 ference in the model or size of the instrument wiU'depend upon 

 the specialties of different cases, and the forms of specula which 

 these may demand. Indeed, the same instrument may serve 

 equally for the great majority of cases of disease affecting 

 the rectal and uterine passages. I confine myself to the de- 

 scription of one of these forms of apparatus, that adapted to 

 the examination of the rectum. The first portion, which I 

 have thought it unnecessary to delineate, is a glass cylinder 

 open at both extremities. This is to be employed by the 

 patient as the medium for a jet of water from the syringe in 

 common use, by which thorough ablution and exposure of the 

 diseased surface is to be effected. The second portion of ap- 

 paratus, represented in two aspects. Figs. 1 and 2, is more 

 complicated, and consists of a metallic speculum («), having 

 a glass tube (6) concealed within. This tube is not open at 

 its farther extremity, but is made to terminate in a smooth 



