200 EXAMINATION AND PRESERVATION MEDIA. 



delicate elements are perfectly preserved in it ; the addition 

 of a drop of osmic acid or corrosive sublimate does not cause 

 the least turbidity and enhances its fixing action. 



371. Tannin (CAENOY, 1. c.) 



Water 100 grammes. 



Powdered tannin ..... 0'50 



372. Picro-Carmine. Picro-carmine has been recommended byRanvier 

 as a medium for teasing fresh tissues in, in the belief that it possesses suffi- 

 cient fixing action to preserve the forms of cells. Carnoy finds that cells live 

 in it for a considerable time, and become gorged with water and deteriorated 

 to a considerable degree. Unfortunately, too, picro-carmine cannot be com- 

 bined with a good fixing agent, as it is precipitated by alcohol and by acids, 

 and especially by osmic acid. 



373. Methyl Green. See under STAINING AGENTS. The 

 aqueous solution is sometimes very useful as an examination 

 medium for fresh tissues. It should be taken fairly concen- 

 trated, in which state it has sufficient fixing power, which is 

 enhanced by the addition of a trace of osmic acid. 



374. Wickersheimer's Fluid (Zool Anz., 1879, p. 670; cf. Journ. 

 Roy. Hie. Soc., 1882, p. 427, id., 1880, p. 355 ; and Entqmol. Nachr., 1880, 

 p. 129). This once famous fluid appears to be quite unsuccessful for histo- 

 logical purposes. 



375. Meyer's Salicylic Vinegar Preservative Solutions (Arch, 

 mik. Anat., xiii, 1876, p. 868), " Salicylic vinegar" is a 

 solution of 1 part of salicylic acid in 100 parts of pyroligiieous 

 acid. The pyroligneous acid should be of 1'04 specific gravity, 

 and should be of a pale yellow colour. This product is found 

 in commerce and may be obtained from Herrn J. M. Andreas, 

 Droguerie-Handlung, Frankfurt -a.-M. 



IST FLUID 



One vol. salicylic vinegar to 10 vols. of the following dilute 

 glycerin : viz. glycerin 1 vol., water 2 vols. 



For various Larva3, Hydrae, Nematodes, &c. 



2ND FLUID 



One vol. salicylic vinegar to 10 vols. of the following dilute 

 glycerin : viz. glycerin 1 vol., water 4 vols. 



For Infusoria. 



376. Noll's Salicylic Vinegar and Gum Medium (Zool. An?,., 

 1883, p. 472). A mixture of equal vols. of Meyer's second 

 fluid (ante, last formula) and Farrant's medium (post, 379). 



