CHLORIDES ORGANIC ACIDS ETC. 43 



The iodide of potassium process should be employed with care, 

 for the iodide may partly redissolve the precipitated compounds 

 formed by the sublimate with the albumens, etc., of the tissues, 

 and it may be well not to begin adding the iodine till the objects 

 have been brought into fairly strong alcohol, 70 or 80 per cent. 



It is important that the sublimate be thoroughly removed from 

 the tissues, otherwise they become brittle, and will not stain so 

 well. They may also become brittle if they are kept long in 

 alcohol. 



It may happen that if the extraction of the excess of sublimate 

 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. 479) 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. Schaper {Anat. Anz., xiii, 1897, p. 463), 

 however, has shoicti that neglect to extract the sublimate from the 

 tissues in bulk may give birth to serious artifacts, zvhich appear to 

 arise during the imbedding process. So also Loyez {Arch. Anat. 

 Micr., viii, 1905, p. 71). Heidenhain {Zeit. wiss. Mik., xxv, 1909, 

 p. 398) removes the iodine from sections by means of sodium 

 thiosulphate. 



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

 liarly brilliant after sublimate. 



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

 produce precipitates that may hurt the preparations. To mani- 

 pulate the objects, wood, glass or platinum may be used ; for 

 dissecting them, hedgehog sjjines, or quill pens, or cactus spines. 



When jjroperly employed, sublimate is for general work un- 

 doubtedly 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 work it is, according to our experience, not to be 

 trusted unless with osmic acid, and only to be recommended where 

 more precise fixing agents are contra-indicated by reason of their 

 lack of penetration, or the like. Amongst other defects it has that 

 of frequently causing very serious shrinkage of cells. 



69. Sublimate with Salt. A solution containing 5 grms. sublimate, 

 0-5 grm, sodium chloride, and 100 c.e. water has been quoted as " solu- 

 tion of Gaule." 



A I per cent, aqueous solution of sodium chloride saturated whilst 

 hot with sublimate was much recommended by Heidenhain (Fest- 

 schrift f. Koelliker, 1892, p. 109). 



