FIXING AND PRESERVATIVE MEDIUMS 55 



disadvantage, but if the specimen be removed from the solution 

 and placed in clean cold water, constantly changed, the stain 

 will gradually disappear without in any way interfering with 

 the preservation, and this in spite of the fact that Lee says : 

 " Bichromate objects have an ugly yellow colour which cannot 

 be removed by soaking in water." ' Subsequently, however, 

 he writes (p. 473) : — 



" Sulphurous Acid as a Bleaching Agent. — Professor Gilson 

 writes me that alcoholic solution of sulphurous anhydride (SO^) 

 is very convenient for the rapid decoloration of bichromate 

 objects. A few drops suffice." 



Further, it is stated that decolorisation takes place by 

 washing the subject for a few minutes in chloral hydrate of 

 I per cent., but probably this treatment may have a deleterious 

 effect upon the tissues. Lo Bianco states that decolorisation 

 is effected also by the addition of a few drops of concentrated 

 sulphuric acid to the alcohol in which the specimens rest, 

 which is practically the same as Professor Gilson's formula. 



All subjects, during the process of hardening in this liquid, 

 should be kept in the dark for some time, and the solution 

 changed if it becomes offensive or charged with blood. Al- 

 though it is stated by Fol {vide Lee) to be worthless for the 

 preservation of mammalian embryos, yet it is most efficient 

 for the preservation of brains, if properly injected and the 

 usual precautions taken. 



It must be borne in mind, however, that both the pre- 

 servative and the water used subsequently are peculiarly liable 

 to become mildewed, and to prevent this it is necessary to add 

 bichloride of mercury in the proportion given in Formula 10. 

 In a former work, the author recommended the addition of a 

 few drops of carbolic acid (CeHjHO) — known also as phenol, 

 phenic acid, phenic alcohol, and hydrate of phenyl, — but, unless 

 used in so great a quantity as to shrivel the specimens, it is of 



