178 SERIAL SECTION MOUNTING. 



dry on the gura film, and then breathe on it until the gum has 

 become sticky. 



A very neat method for cases in which it is not required to 

 treat the slide with watery fluids. 



WADDINGTON (Journ. Quek. M. Club, vi, 1881, p. 199 ; Journ. Roy. Mic. 

 Soc. (N.S.), i, 1881, p. 704) gives the following process for preparing 

 " Arabin," a purified gum arable which has the advantage of not presenting 

 a granular appearance under the microscope as ordinary gum arabic does. 



Dissolve clear and white gum arabic in distilled water to the consistency 

 of thin mucilage. Filter. Pour the filtrate into rectified alcohol, and shake 

 well ; the arabin separates as a white pasty mass. Place it on filter paper 

 and wash with pure alcohol until the washings are free from water. Dry. 



The white powder thus obtained should be dissolved in distilled water and 

 filtered twice. It may then be placed on slides, which are drained, dried, 

 and put away till wanted. In this condition it may be preserved indefinitely. 



320. Frenzel's Gum Method (Arch. f. mik. Anat., Bd. xxv, 

 1885, p. 51). Gum arabic is dissolved in water to the consis- 

 tency of a thin mucilage, and to this is added aqueous solution 

 of chrome-alum. An excess of the latter does no harm. 

 Finally, add a little glycerin and a trace of alcohol (1. c., p. 142). 

 The slide is prepared with this in the usual way, the sections 

 (either cut dry or in the wet way) are gently pressed on to it 

 with a brush and slightly melted on, and heated for at most a 

 quarter of an hour at a temperature of 30 to 45 C., which 

 suffices to render the gum insoluble. This layer has the ad- 

 vantage of not staining with the majority of staining-fluids ; 

 fuchsin and safranin are the only ones that stain it to a 

 harmful degree. In the other anilins, and in carmine or 

 haematoxylin, it does not stain. Watery stains (it is stated) 

 may be used with it. 



321. Born and Wieger's Quince-Mucilage (Zeit. f. wiss. Mik. } 

 1885, p. 346). To two volumes of the ordinary pharmaceutical 

 quince-mucilage add one volume of glycerin and a trace of 

 carbolic acid. Spread in a thin layer on a carefully cleaned 

 slide, and arrange the sections on the moist surface. Heat 

 for twenty minutes at a temperature of 30 to 40 C. After 

 removal of the paraffin by turpentine the slide is brought 

 for half an hour into absolute alcohol. You may then mount, 

 or pass through successive alcohols, and stain. Alkaline 

 staining fluids must be avoided, as they soften the mucilage 

 and cause the sections to become detached. 



