126 EXPERIMENTS FOR INTERPRETATION [Cn. IV 



(10) Try staining the preparations to be studied in various ways 

 to bring out the structural details; remember also the advantage of 

 a color picture over a pure refraction image ( 137) and especially of 

 a combined color and refraction image. Keep in mind also that the 

 microscopic image cannot be expected to reveal structural details 

 that are not in some way clearly differentiated in the specimen. 



(n) If artificial light must be used, employ a screen of daylight 

 glass ( 92) between the source of illumination and the microscope; 

 then one can obtain true color effects. 



(12) The composite picture derived from all available means of 

 observation is much more likely to be correct than that obtained by 

 only one or two means of observation. 



(13) According to Wright, p. 46, it is far more difficult to prepare 

 and properly illuminate a specimen than to get a good image of it 

 after it is thus prepared and lighted. 



COLLATERAL READING FOR CHAPTER IV 



For general discussions: Carpenter-Dallinger; A. E. Wright, Principles of 

 Microscopy, Ch. V; Beale; Spitta, Microscope, Ch. XVIII; Chamot, Chemi- 

 cal Microscopy. 



For pedesis see Jevons in Quart. Jour. Science, n.s., Vol. VIII (1878), p. 167; 

 Rutherford, Science, N. S. Vol. XXX, 1909, pp. 289-302. For the original 

 account of this see Robert Brown, "Botanical appendix to Captain King's 

 voyage to Australia," Vol. II, p. 534 (1826). 



For overcoming pedesis for photography see Gage, The use of a solution of 

 gelatin to obviate pedesis in photographing milk globules and other minute 

 objects in water, Transactions Amer. Micr. Soc., Vol. XXIV, 1902, p. 21. 



For figures (photo-micrographs, etc.) of the various forms of starch, see 

 Bulletin No. 13 of the Chemical Division of the U. S. Department of Agri- 

 culture. For hair and wool, see Bulletin of the National Association of Wool 

 Growers, 1875, P- 47; Proc. Amer. Micro. Soc., 1884, pp. 65-68; Herzfeld, 

 translated by Salter, The technical testing of yarns and textile fabrics, London, 

 1898. 



For different appearances due to the illuminator, see Nelson, in Jour. Roy. 

 Micr. Soc., 1891, pp. 90-105; and for the illusory appearances due to diffrac- 

 tion phenomena, see Carpenter-Dallinger, p. 434; Mercer, Trans. Amer. 

 Micr. Soc., V. 18 p. 321-396; also, A. E. Wright's Principles of Microscopy, 

 especially the first five chapters; and chapter IX and the appendix. Conrad 

 Beck. The Theory of the Microscope. Cantor Lectures before the Royal 

 Society of Arts, Nov. Dec., 1907. 59 pages, London, 1908. 



