File:An American text-book of physiology (1897) (14780082271).jpg

Identifier: americantextbook00howe (find matches)
Title: An American text-book of physiology
Year: 1897 (1890s)
Authors: Howell, William H. (William Henry), 1860-1945 Bowditch, H. P. (Henry Pickering), 1840-1911
Subjects: Physiology
Publisher: Philadelphia : Saunders
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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pectra.—Solutions of haemoglobin and its derivative com-pounds, when examined with a spectroscope, give distinctive absorption bands.A brief account of the principle and arrangement of the spectroscoi)e, althoughunnecessaiy for those familiar with the elements of Physics, is given by wayof introduction to the description of these absorption bands. Light, when made to pass through a glass prism, is broken up into its constituentrays, giving the play of rainbow colors known as the spectrum. A spectroscope isan apparatus for producing and observing a spectrum. A simple form, which illus-trates sufficiently well the construction of the apparatus, is shown in Figure 87, Pbeing the glass prism giving the spectrum. Light falls upon this prism throughthe tube (a) to the left, known as the collimator tube. A slit at the end of thistube (s) admits a narrow slice of light—lamplight or sunlight—which then, bymeans of a convex lens at the other end of the tube, is made to fall upon the prism
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Fig. 86.-Cr)-stallized htemoglobin (after Frey):a, h, crystals from venous blood of man; e, fromthe blood of a cat; d, from the blood of a BLOOD. 339 (p) with its rays parallel. In passing through the prism the rays are dispersed byunequal refraction, giving a spectrum. The spectrum thus produced is examined bythe observer with the aid of the telescope («). When the telescope is properly focussedfor the rays entering it from the prism (p), a clear picture of the spectrum is seen. Thelength of the spectrum will depend upon the nature and the number of prisms throughwhich the light is made to pass. For ordinary purposes a short spectrum is preferablefor haemoglobin bands, and a spectroscope with one prism is generally used. If thesource of light is a lamp-flame of some kind, the spectrum is continuous, the colorsgradually merging one into another from red to violet. If sunlight is used, the spectrumwill be crossed by a number of narrow dark lines known as the Fraunhofer lines KALEVIMAG

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