704 Methods of Microscopical Research [September, 



three to four days for the action of the fluid. Dr. Eisig has used 

 this fluid with great success in preparing the delicate lateral or- 

 gans of the Capitellidae for sections, and recommends it strongly 

 for other annelids. Dr. Eisig allows objects to remain 3-5 hours 

 in the fluid, then transfers to 70 per cent, alcohol. With small 

 leeches I have found one hour quite sufficient, and transfer to 50 

 per cent, alcohol. 



8. Corrosive Sublimate. — Prompted by a statement found in an 

 old paper by Blanchard, 1 Dr. Lang began experimenting with 

 corrosive sublimate as a medium for killing marine Planarians, 

 and his marked success led him and others to employ the same 

 with other animals. In most cases Dr. Lang now uses a saturated 

 solution of c<; .water. A saturated solution in 



picro-sulphuric acid, which in some cases gives better results if a 

 little acetic acid (5 per cent, or less) is added, is also used. 2 

 Blanchard's mode of treatment was to mix a .quantity of the 

 aqueous solution with the sea water, and thus poison the animals. 

 Dr. Lang, on the contrary, removes the sea water so far as possi- 

 ble before applying the solution. With Planarians he proceeds 

 in the following manner: 



The animal is laid on its back and the water removed with a 

 pipette, the solution being then poured over it, it dies quickly and 

 remains fully extended. After half an hour it is washed by 

 placing it in water and changing the water several times during 

 thirty minutes. It is next passed through 50 per cent., 70 per 

 cent., 90 per cent, and 100 per cent, alcohol. In two days it is 

 fully hardened, and should then be stained and imbedded in par- 

 affin as early as possible, as it is liable to become brittle if left long 

 in alcohol. The time required by the corrosive sublimate varies 

 with different objects, according to size and the character of the 

 tissues. As a general rule, it may be said that objects should be 

 removed from the fluid as soon as they have become thoroughly 



1 " Recherches sur l'Organisation des Vers," by Emile Blanchard. Ann. des Sci. 

 Nat. Zoo]. Ser. 3, t. viu, 1847, P- 247- 



