File:An American text-book of physiology (1897) (14760233826).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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-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
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Fig.87.—Spectroscope: p, the glass prism ; a, the collimator tube, showing the slit (s) through which thelight is admitted ; b, the telescope for observing the spectrum. (see PI. I., Fronthpiece, for an illustration in colors of the solar spectrum). The position ofthese lines in the solar spectrum is fixed, and the more distinct ones are designated by lettersof the alphabet, A, b, c, d, e, etc., as shown in the charts below. If while using solarlight or an artificial light a solution of any substance which gives absorption bands isso placed in front of the slit that the light is obliged to traverse it, the spectrum asobserved through the telescope will show one or more narrow or broad black bands,which are characteristic of the substance used and which constitute its absorption spec-trum. The positions of these bands may be designated by describing their relations tothe Fraunhofer lines, or more directly by stating the wave-lengths of the portions of thespectrum between which absorp

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