202 EXAMINATION AND PRESERVATION MEDIA. 



To which after twelve hours are added 



Glycerin! . . . . . .5*0 



Sol. aquosa acid, carbol. (5-100) . . lO'O 

 Marine animals may be preserved in this by simply run- 

 ning in a drop under the cover, and next day or later adding 

 what is necessary to make up for evaporation, and closing the 

 mount. Shrinkage is very slight, and most colours keep well. 



381. Cole's Gum and Syrup Medium (see above, 309). 



382. Fabre-Domergue's Glucose Medium (La Nature, No. 823, 

 9 Mars, 1889, supp.). 



Glucose syrup diluted to twenty-five degrees of the areo- 

 meter (sp. gr. 1-1968) . . ' . 1000 parts. 

 Methyl alcohol ... 200 



Glycerin 100 



Camphor, to saturation. 



The glucose is to be dissolved in warm water, and the other 

 ingredients added. The mixture, which is always acid, must 

 be neutralised by the addition of a little potash or soda. 



This medium is said to preserve without change almost all 

 animal pigments. If it really performs this, its great value is 

 evident. 



Glycerin Media. 



383. Glycerin. Glycerin diluted with water is frequently 

 employed as an examination and mounting medium. Dilution 

 with water is sometimes advisable from an optical point of 

 view, on account of the increased visibility that it gives to 

 many structures by lowering the index of refraction of the 

 glycerin. But from the point of view of efficacious preserva- 

 tion, it is always advisable to use undiluted glycerin, the 

 strongest that can be procured. 



Long soaking of tissues in glycerin of gradually increased 

 strength is a necessary preliminary to mounting in all cases 

 in which it is desired to obtain the best possible preparations 

 and to ensure that they shall keep well, if this soaking is 

 done on the slide (the cover being removed and the object 

 treated with fresh glycerin every one or two days), it is well 

 to take the precaution recommended by Beale, of luting the 

 edges of the cover so as to make the preparation air-tight, as 



