296 CORROSION, DECALCIFICATION, AND BLEACHING. 



out previous removal of the spicula. The spicula appear to "be cut ; probably 

 they break very sharply when touched by the knife. Knives are of course- 

 not improved by cutting such sections. 



Bleaching. 



575. MAYER'S Chlorine Method (Mitth. Zool. Stat. Neapel, ii, 

 1881, p. 8). This is a process imagined for the purpose of 

 getting rid of the blackening that often occurs as a conse- 

 quence of treatment by osmic acid. 



The specimens are put into alcohol (either of 70 or 90 per 

 cent.). Crystals of chlorate of potash are added until the 

 bottom of the vessel is covered with them. A few drops of 

 concentrated hydrochloric acid are then added by means of a 

 pipette, -and mixed in by shaking the vessel as soon as the 

 green colour of the evolving chlorine has begun to show itself. 

 Warm if necessary ; but most objects, even large ones, may be 

 bleached in half a day without the employment of heat. The 

 tissues do not suffer. 



Instead of hydrochloric acid, nitric acid may be used ; in 

 which case the bleaching agent is the freed oxygen, instead 

 of chlorine. 



The first method may be used for the purpose of removing 

 pigment from the eyes of insects. 



576. MARSH'S Chlorine Method (Section Cutting, p. 89). 

 Marsh generates chlorine in a small bottle by treating crystals 

 of chlorate of potash with strong HC1, and leads the gas (by 

 means of a piece of glass tubing bent twice at right angles) 

 to the bottom of a bottle containing the sections in water. 

 (See a fig. of the apparatus in Journ. Roy. Mic. 8oc., iii, 1880,. 

 p. 854.) 



577. Chlorine Solution (SABGENT'S method). Hydrochloric acid, 1O 

 drops ; chlorate of potash, \ dr. ; water, 1 oz. Soak for a day or two. Wash 

 well. 



This method is intended for " bleaching insects ; " it will be seen that it is- 

 only applicable to the preparation of hard pails, as soft tissues would be de- 

 stroyed by the solution. 



578. Kreasote (POUCHET'S method, Journ. de I'Anat., 1876, p. 8, etseq.). 

 I gather from the paper here quoted that most of the granular animal 

 pigments are soluble in kreasote. Other solvents are mentioned in this 

 paper (" On the Change of Coloration through Nervous Influence"), but 

 this appears to be the only one capable of general histological application. 



