FIXING AND HARDENING AGHNTS. 47 



It may happen that if the extraction of the excess of sub- 

 limate from the tissues in bulk has been insufficient, crystals 

 may form in the sections after they have been mounted in 

 balsam. This may easily be prevented by treating the 

 sections themselves with tincture of iodine for a quarter of 

 an hour before mounting. Some workers hold that this does 

 away with the necessity of treating the tissues in bulk with 

 iodine, which is frequently a very long process. Thus, Mann 

 {Zeit. wiss. Mik,, xi, 1894, p. 479j prefers treating the sections 

 rather than the tissues in bulk, on the ground that the 

 iodine makes them soft, so that they shrink on coming into 

 paraffin. Schapee {Anat. Anz., xiii, 1897, p. 463), however, 

 has shown that neglect to extract the sublimate from the 

 tissues in bulk may give birth to serious artefacts, which 

 appear to arise during the imbedding process. So also 

 LoTEZ {Arch. Anat. Micr., viii, 1905, p. 71). Heidbnhain 

 [Zeit. wiss. Mile, xxv, 1909, p. 398) removes the iodine from 

 sections by means of sodium tliiosulphate. 



You may stain in any way you like. Carmine stains are 

 peculiarly brilliant after sublimate. 



The solutions must not be touched with iron or steel, as 

 these produce precipitates that may hurt the preparations. 

 To manipulate the objects, wood, glass or platinum may be 

 used; for dissecting them, hedgehog spines, or quill pens, or 

 cactus spines. 



When properly employed, sublimate is for general work 

 undoubtedly a most useful fixing agent. It is applicable to 

 most classes of objects. It is perhaps less applicable, in the 

 pure form, to Arthropods, as it possesses no great power of 

 penetrating chitin. For cytological ivorh it is, according to 

 my experience, not to be trusted, and only to be recom- 

 mended where more precise fixing agents are counter-indi- 

 cated by reason of their lack of penetration, or the like. 

 Amongst other defects it has that of frequently causing very 

 serious shrinkage of cells. 



64. Sublimate with. Salt. — A sokition containing 5 g. sublimate, 

 0-5 g. sodium chloride, and 100 c.c. water has been quoted as "solution 



of GrABXE." 



A one-half per ceijt. aqueous solution of sodium chloride saturated 

 whilst hot with siiblimate was much recommended by Heidbnhain 

 {Festschrift f, KoelUher, 1892, p. 109). 



