872 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Professor Merkel,* who employed a mixture of these two solutions 

 in equal parts for the retina, states that he allowed from three to 

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

 with great success in preparing the delicate lateral organs of the 

 Capitellidse 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 Mr. 

 Whitman has found one hour quite sufficient, and transfer to 50 per 

 cent, alcohol. 



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

 old paper by E. Blanchard,f 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 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.J 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 imbedded 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 by it. In order to kill 

 more quickly than can sometimes be done at the ordinary tempera- 

 ture, 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, Gephy- 

 reans, Balanoglossus, Echinoderms, Sagitta, Annelids, Ehabdocoela, 

 Dendrocoela, Cestodes, Trematodes, embryos and adult tissues of 

 Vertebrates and, according to Mayer and Giesbrecht, Crustacea with 

 thin chitinous envelopes, e. g. Sapphirina, Copepods and larvae of 

 Decapods. With the Arthropoda good results have not been ob- 

 tained. 



* ' Ueber die Macula lutea des Menschen,' &c, Leipzig, 1870, p. 19. 



t Ann. Sci. Nat. Zool., viii. (1874) p. 247. 



% These solutions are given in Zoolog. Anzeiger, ii. (1879) p. 46. The original 

 solution (Zoolog. Anzeiger, i. (1878) pp. 14-15, this Journal, i. (1878) p. 256) 

 now little used, stood thus : — Distilled water, 100 parts ; common salt, 6-10 

 parts ; acetic acid, 5-8 parts ; corrosive sublimate, 3-12 parts ; alum (in some 

 cases) \ part. 



