CHAPTER XXVI. 297 



overnight in a freshly-made mixture of equal parts of absolute alcohol 

 and strong F lemming. Wash out for two days in 50 per cent, alcohol, 

 imbed in celloidin, stain in Best's carmine. 



See also CREIGHTON, The Formative Property of Glycogen, London, 

 1896 ; GAGE, Trans. Amer. Micr. Soc., xxviii, 1908, p. 203 ; KATO, 

 Arch. Ges. Pliys., cxxvii, 1909, p. 125 ; BUSCH, Arch. Intern. Phys., iii, 

 1905, p. 51 ; MAYER, Zeit. wiss. Mikr., xxvi, 1909, p. 513 ; ARNOLD, 

 Sitzb. Heidelberg. Acad. Wiss., 1909, p. 1, 1910, p. 3, and 1911, 14 Abh. ; 

 Arch. path. Anat., cxciii, 1908, p. 175 ; Arch. mik. Anat., Ixxiii, 1909, 

 p. 265; Ixxvii, 1911, p. 346; Beitr. path. Anat., li, 1911, p. 439; 

 FRAENKEL, Virchow's Arch., 1911, p. 197 ; NEUBERT, Beitr. path. Anat., 

 xlv, 1909, p. 38 ; ERHARD, Arch. Zellforsch., viii, 1912, pp. 447 and 507 ; 

 EHRLICH and LAZARUS, Die Anaemic, 1898, p. 30 ; PEKELHARING, 

 Petrus Camper, Deel I, 1901, p. 231 ; DRIESSEN, Zeit. wiss. Mik., xxii, 

 1905, p. 422 ; FISCHER, Anat. Anz., xxvi, 1905, p. 399 ; FIESSINGER, 

 C. R. Soc. Biol., Ixvi, 1909, p. 183 ; NETJKIRCH, Arch. path. Anat., cc, 

 1910, p. 82. 



650. Some Microchemical Tests. IRON. Organic compounds of 

 iron, which are not ionisable into ferric and ferrous ions, and in which 

 the iron cannot be detected by the ordinary reagents, are much 

 more frequently present in animal and vegetable tissues than was 

 previously believed to be the case. In addition to the albuminate 

 compounds, there exist iron compounds giving ferric and ferrous 

 ions, detectable with the ordinary reagents, and which, for con- 

 venience, may be designated Inorganic Iron Compounds. 



The nature of many of the compounds of iron found in placentas, 

 blood-organs, the liver, etc., is obscure ; many of them appear to 

 be formed as degeneration or excretion products, from the breaking 

 down of haemoglobin. See below. 



Most of our knowledge of the methods for the detection of iron 

 in tissues and cells is due to A. B. MACALLUM (Quart. Journ. 

 Micr. Science, xxxviii, 1895 ; Journ. Physiology, 1897 ; Ergebn. d. 

 Physiol. Wiesbaden, 1908). Macallum has shown that, to detect 

 organic iron, one must convert it into inorganic. This can be done 

 by allowing sulphuric or nitric acid alcohol to act upon sections, or 

 a piece of tissue, for from one to twenty-four hours at 35 C., accord- 

 ing to the strength of acid and the size of the object. When masked 

 iron is liberated in the tissues by acid alcohol, most of it is in the 

 form of ferric salts, particularly when the oxidising nitric acid is 

 used, and a small part occasionally of ferrous compounds. Inorganic 

 iron compounds in tissues are usually ferric, more rarely ferrous 

 salts. 



The commonest tests for iron in tissues are the Prussian blue 

 reaction, and Macallum's hsematoxylin. The latter test should never 



