106 MICROSCOPICAL KKSEARCH IN THE 



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

 solution of corrosive sublimate in 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. * 

 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 possible 

 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 embedded in paraffin 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 

 saturated with it. In order to kill more quickly than can sometimes 

 be done at the ordinary temperature, the solution is heated, and in 

 very difficult cases may be used boiling. 



Corrosive sublimate has been used with success by Dr. Lang 

 and others in the following cases : — Hydroids, corals, Nemertines, 

 Gephyrea, Balanoglossus, Echinoderms, Sagitta, Annelids, Rhab- 

 docoela, Dendrocoela, Cestodes, Trematodes, embryos and adult 

 tissues of Vertebrates and, according to Mayer and Giesbrecht, 

 Crustacea with thin chitinous envelopes — e.g.^ Sapphirina, Cope- 

 pods and larvae of Decapods. 



* These solutions given in Zoolog. Anzeiger, 1879, 11, p. 46. 



The original solution {Zoolog. Anzeiger, 1878, i, p. 14—15), now little used, 

 stood thus : — 



Distilled water 

 Common salt 

 Acetic acid 

 Corrosive sublimate 

 Alum (in some cases) 



100 parts. 



6 — 10 



5-8 



3—12 



¥2 



