File:A text-book of physiology - for medical students and physicians (1916) (14583822677).jpg

Identifier: textbookofphysio1916howe (find matches)
Title: A text-book of physiology : for medical students and physicians
Year: 1916 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Medicine
Publisher: Philadelphia and London : W. B. Saunders Company
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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of this tube (S) admits a narrow slice of light—•lamplight or sunlight—which then, by means of a convex lens at the otherend of the tube, is made to fall upon the prism (P) with its rays parallel. In * Reichert and Brown, The Crystallography of Hemoglobins, CarnegieInstitution of Washington, No. 116, 1909. t Uhlik, Archiv f. d. gesammte Physiologie, 104, 64, 1904. 432 BLOOD AND LYMPH. passing through the prism the rays are dispersed by unequal refraction, givinga spectrum. The spectrum thus produced is examined by the observer withthe aid of the telescope (B). When the telescope is properly focused for therays entering it from the prism (P), a clear picture of the spectrum is seen.The length of the spectrum will depend upon the nature and the number ofthe prisms through which the light is made to pass. For ordinary purposes ashort spectrum is preferable for hemoglobin bands, and a spectroscope with oneprism is generally used. If the source of light is a lamp flame of some kind,
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Fig. 182.-—Spectroscope: P, The glass prism; A, the collimator tube, showing the slit, iS,through which the light is admitted; B, the telescope for observing the spectrum. the spectrum is continuous, the colors gradually merging one into anotherfrom red to violet. If sunlight is used, the spectrum will be crossed by anumber of narrow dark lines known as the Fraunhofer lines. The positionof these lines in the solar spectrum is fixed, and the more distinct ones aredesignated by letters of the alphabet, A, B,C, D, E, etc., as shown in the chartsbelow. If while using solar light or an artificial light a solution of any sub-stance which gives absorption bands is so placed in front of the slit that thelight is obliged to traverse it, the spectrum as observed through the telescopewill show one or more narrow or broad black bands that are characteristicof the substance used and constitute its absorption spectrum. The positionsof these bands may be designated by describing their relations to

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