32 FIXING AGENTS. 



as soon as fixed, that is, in other words, as soon as they are 

 seen to have become opaque throughout, which is practically as 

 soon as they are penetrated by the liquid. Small objects are 

 fixed in a few minutes. I have found that a " salivary " gland 

 of the larva of Chironomus is thoroughly fixed in three seconds. 



Wash out with water or with alcohol. I consider alcohol 

 almost always preferable. Alcohol of about 70 per cent, may 

 be taken. The extraction of the sublimate is hastened by the 

 addition of a little camphor to the alcohol. Or a little tincture 

 of iodine may be added to the liquid, either alcohol or water,, 

 used for washing, and the liquid changed until it no longer 

 becomes discoloured by the objects. It is important that the 

 sublimate be thoroughly removed from the tissues, otherwise 

 they become brittle. They will also become brittle if they 

 are kept long in alcohol. 



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

 peculiarly brilliant after sublimate, owing to the formation of 

 mercuric carminate. It is not necessary that the objects be 

 thoroughly washed out before staining ; the staining processes 

 themselves may be made to constitute a part of the washing- 

 out process. 



It must be remembered that 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, hedge- 

 hog spines, or quill-pens. 



When properly employed, sublimate is undoubtedly a fix- 

 ing agent of the very highest order. 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. 



Before passing to the sublimate mixtures that have been 

 recommended, it must here be stated that for general purposes 

 there seems to be no use in adding anything except a little 

 acetic acid to the pure sublimate. 



46. Corrosive Sublimate (LANG'S formula, ' Zool. Anzeiger,' 1878, i, 

 p. 14). For Planaria. Take 



Distilled water . . 100 parts by weight. 



Chloride of sodium . . 6 to 10 parts. 



Acetic acid . . . 6 to 8 ., 



Bichloride of mercury . 3 to 12 



(Alum, in some cases, . i). 



