METHYLEN BLUE 197 



(The objects that have been treated with one of the sohitions of the 

 sodium salt are not thoroughly resistant to alcohol, so that for 

 them it is well to cool the alcohol to inider 15° C.) Sections may 

 be after-stained with alum carmine, or " neutral " tar colours. 



Slight modifications of this method are given by Uogiel 

 {Arch. mik. Anat., 1897, p. 772 ; 1898, p. 237 ; Zeit. wiss. 

 ZooL, Ixvi, 1899, p. 361 ; and Enzyk. mik. Technik., 1903, 

 p. 825, and 1910, p. 108). He omits the peroxide, the hydro- 

 chloric acid, and the cooling. Bethe {Zeit. wiss. Mik., xvii, 1900, 

 p. 21) does not approve of these modifications. 



Further modifications of the molybdenum method have been 

 published by Leontowitsch {Intern. Monatsschr. Anat., xviii, 

 1901, p. 142). 



MiCHAiLOW {Zeit. wiss. Mik., xxvii, 1910, p. 19) adds to 8 per 

 cent, solution of molybdate 0-5 per cent, of formalin, leaves the 

 objects in a large quantity of it (filtered) for twenty-four hours 

 at 37° C, washes with warm water, and passes through alcohol 

 and xylol into xylol-damar (not balsam). 



See also Schmidt {Arch. Ges. Phys., ciii, 1906, p. 522). 



Harris {Philadelphia Medical Journ., May 14th, 1898), after 

 staining, rinses with water, and brings into a saturated solution 

 of either ferrocyanide or ferricyanide of potassium which has 

 been cooled to within a few degrees of zero (a trace of osmic 

 acid may be added to prevent maceration). They remain therein 

 for from three to twenty-four hours, and are then washed in 

 distilled water for an hour, and are dehydrated in absolute alcohol 

 kept at a low temperature, cleared in xylol or cedar oil, and 

 imbedded in paraffin. 



384. Impregnation of Epithelia, Lymph-spaces, etc. (Dogiel, 

 Arch. mik. Anat., xxxiii, 1889, pp. 440 et seq.). Suitable pieces of 

 tissue (thin membrane by preference) are brought fresh into a 4 

 per cent, solution of methylen blue in physiological salt solution 

 (in the Encycl. mik. Technik., 1903, p. 827, Dogiel gives the strength 

 of the methylen blue as \ to 1 per cent.). After a few minutes 

 therein they are brought into saturated solution of picrate of 

 ammonia, soaked therein for half an hour or more, then washed in 

 fresh picrate of ammonia solution, and examined in dilute glycerin. 



If it be wished only to demonstrate the outlines of endothelium 

 cells, the bath in the stain should be a short one, not longer than 

 ten minutes in general ; whilst if it be desired to obtain an impreg- 

 nation of ground-substance of tissue, so as to have a negative 

 image of other spaces, the staining should be prolonged to 

 fifteen or thirty minutes. 



If it be desired to preserve the preparations permanently, they 

 had better be mounted in glycerin saturated with picrate of 

 ammonia, or {Enzyk., 1910, ii, p. 110) fixed with anunonium 

 molybdate and a trace of osmium. 



