368 CONNECTIVE TISSUES. 



extract of Alkanna in 96 per cent, alcohol, and mounting in glycerin 

 or syrup. 



LORRAIN SMITH (Journ. Path. Bact., xii, 1907, p. 1) finds that 

 Nile blue stains fatty acids blue and neutral fats reddish. 



Similarly EISENBERG (Virchow's Arch., cxcix, 1910, p. 502), who 

 recommends aqueous solution of Nilblau BB. 



BENDA (ibid., clxi, 1900, p. 194) finds that free fatty acids can be 

 detected by Weigert's neuroglia mordant. See also BERNER, ibid., 

 clxxxvii, 1907, p. 360, and FISCHLER, Zeit. wiss. Mik., xxii, 1905, 

 p. 263. 



OK A JIM A (ibid., xxix, 1912, p. 67) extracts red capsicum berries 

 for some days with alcohol, and evaporates down to one fifth. This 

 stains only fatty bodies : amongst them, myelin. 



See also KINGSBURY, Anat. Rec., v, 1911, p. 313. 



770. Removal of Fatty Substances. If not treated with osmic 

 acid or mordanted with strong bichromate, alcohol, ether, chloroform, 

 pyridine, xylol, will readily dissolve fatty substances. Osmicated fats 

 and lipoids are more resistant, especially if osmic acid and bichromate 

 have been combined. It can then be removed in a few hours by 

 alcoholic hydrogen peroxide (10 per cent. H 2 2 in 80 per cent, alcohol) 

 or in twenty-four hours by oil of turpentine. Ether, creosote, xylol, 

 clove oil and chloroform will also remove osmicated fats and lipoids if 

 allowed to act sufficiently lone;. 



See also FLEMMING in Zeit. wiss. Mikr., 1889, pp. 39, 178. 



771. Differentiation between Fats and various Lipoids. Fix in for- 

 mol and prepare frozen sections. Stain some with Sudan or Scharlach 

 (see above 769), others with osmic acid. Leave some unstained. 

 Globules which stain with Sudan or Scharlach and osmic acid, and 

 which in unstained sections show no double refraction, can be identified 

 with certainty as true fats. This may be confirmed in paraffin sections 

 by fixing in bichromate and subsequent treatment with osmic acid as 

 in the methods of Schridde and Marchi. These globules should then 

 reduce osmic acid. But the presence of double refraction must not be 

 taken as excluding the presence of true fats since the globules may be a 

 mixture of true fats and double refracting lipoids. The deduction that 

 true fats are absent can be made when tissue containing fatty material 

 as indicated by blackening with osmic acid fails to give this blackening 

 after previous treatment with bichromate, as for instance in normal 

 peripheral nerve. 



The histochemical differentiation between true fats and lipoids is 

 much more difficult when these substances are mixed in one and the 

 same globule than when one cell contains several globules of which 

 some are composed entirely of true fats while others contain lipoids. 

 In the latter case methods may be applied which depend on differences 

 in the solubility in various solvents. 



DEFLANDBE (Journ. Anat. Phys., 1904, p. 80) fixes in formol of 4 per 



