120 Slaini)}g Procedures (chap. 11) 



Gray and Wess' Medium (PVA) (1952) 



PVA (polyvinyl alcohol) 71-24^ 2.0 gm. 



70% acetone 7.0 ml. 



glycerol 5.0 ml. 



lactic acid 5.0 ml. 



distilled water 10.0 ml. 



Make a paste of the dry alcohol with acetone. Mix half of water with 

 glycerol and lactic acid; stir into paste. Add rest of water drop by 

 drop with stirring. Solution will be cloudy but becomes transparent 

 as warmed in water bath about 10 minutes. 



PVA (polyvinyl alcohol) Mounting Medium 



Add 15.0 gm. PVA 71-24 powder (DuPont. See note below) slowly 

 to 100. ml. cold water. Heat in water bath (80°C) with stirring until 

 the solution becomes as viscous as thick molasses. Filter out undis- 

 solved lumps through two layers of cheesecloth. Solution will appear 

 milky, but after standing for several hours, will clear. A thin film can 

 be spread over stained blood smears when cover glasses are luidesira- 

 ble. 



The following are recommended for small whole mounts, insects, 

 worms, tiny invertebrates and the like. 



Berlese Mounting Medium 



1. gray's formula (1952). 



water 10.0 ml. 



glacial acetic acid 3.0 ml. 



dextrose syrup 5.0 ml. 



gum arable (acacia) 8.0 gm. 



chloral hydrate . 75.0 gm. 



Mix water with acid and syrup; dissolve gum in this. Requires week 

 or more. Stir at intervals. When soliuion is complete, add chloral 

 hydrate. This is one of the best media lor insects. As was suggested 

 for Farrant's medium, it is difficult to obtain good gum. 



2. THICK FORMULA. 



distilled water 40.0 ml. 



saturated aqueous solution of chloral hydrate . . 30.0 ml. 



gum arable (acacia) 25.0 gm. 



glycerol 5.0 ml. 



^ Obtainable from E. L DuFoiit de Neniouvs and Co., Wilmington, Del. 



