Diseases of the larynx / by J. Gottstein ; translated and added to by P. M'Bride.

  • Gottstein, Jacob, 1832-1895.
Date:
[1885?]
Catalogue details

Licence: Public Domain Mark

Credit: Diseases of the larynx / by J. Gottstein ; translated and added to by P. M'Bride. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    method is employed. Mackenzie constructed a lamp with a biconvex lens (rack movement lamp) which admits of every possible perpen- diciilar and hoi-izontal motion, and also a so-called light concentrator which may be adapted to any lamp or even to a candle. It is composed of a small metallic cylinder about 9 cms. in length and 6 cms. in diameter, closed at one end and having at the other a plano- convex lens of about 6*3 cms. in diameter, the plane surface of Avhich is directed towards the light. In the upper and lower surfaces of the cylinder arc situated, opposite to one another, two round openings of about 5*7 cms. in diameter. These are not equidistant from the two extremities of the cylinder, but are placed so near its closed extremity that a perpendicular drawn through their centres is situated at about 6 3 cms. from the plane surface of the lens, and so that rays starting from this point pass in an almost parallel direction. At the lower of these two openings are situated two semicircular arms so adapted that they can be attached by means of a screw to the widest lamp as well as to an ordinary candle or even to a thin glass ttibe. Illumination b}' means of lenses is specially preferred in France ; the light is good, but the method is less simple than the nse of the concave reflector. COMBINATION OF CONCAVE MIRRORS WITH LENSES. In order to produce a larger image, with at least as much lighting power as is arri\'ed at by means of a concave mirror, it has been attempted to concentrate rays, which have passed through a prism, by means of a reflector. If this combination is to be of real use and to project light into the interior of the larynx, then the relation of the lens to the lamp and to the reflector must not be arbitrary but correspond to optical laws. *B. Frankel, who has carefully considered all the various physical conditions relating to this matter^ constructed an apparatus in which he placed the flame in the focus of the lens, which latter had a focal distance of from 10 to 12 cms. As in this case the rays are parallel when leaving the lens, they will be again united to form an image of the flame at 30 cms. by means of a reflector whose focal distance is also 30 cms. The lens may also be placed nearer the flame or may be removed to a point beyond its focal distance. In each case the manner in which the rays leave the lens must be calculated, and according to this the reflector must be chosen. It is useless to use more than one lens—as in Tobold's apparatus, which contains three, and is much employed on account of its convenient arrangement—because the light is much diminished in its * ;5ieni8sen Handbuch dcr Specidlen Patlwlogie und Tfierapie. Bd. IV.