308 THE AMERICAN MONTHLY [Nov., 



water destroyed the colors, by again extracting the gum from 

 the tissues But I am now convinced this is not the case; the 

 action of the gum is to harden the tissues against the softening 

 influence of the glycerine; the real color preserver is the glyce- 

 rine, and it preserves because it excludes air and water. It acts 

 as a solid glass, and the only influence at work to bleach the 

 specimen is light, which, curious to say, as the exhibited speci- 

 mens show, does not seem to have much effect. 



Reflecting on this action it occurred tome: if the exclusion of 

 air and moisture/»is the great ideal to aim at, could not some 

 substance of a lighter specific gravity than glycerine be found? 

 Why not some kind of oil? And of course, in Ceylon cocoanut 

 oil first suggested itself. But cocoanut oil, far from being likely 

 to be a preservative, would require preserving itself. How was 

 this to be done? Would carbolic acid mix with it? I found 

 on experimenting, that carbolic acid mixed with it in all pro- 

 portions. There was of course, no idea of using this as a preser- 

 vative, the specimens must be first prepared. Very fluid 

 arsenic paste was used for silvery fish with some success, and 

 reduced gum and glycerine and gelatine was also tried ; but from 

 the very first it proved a very refractory mounting medium. It 

 was very diflRcult to get a sufficiently white oil to begin with 

 and when I did, it always had a strong tendency to discolor. 

 Time has proved that I need not have troubled myself; it can- 

 not be used as a mounting medium. Mixtures of carbolic acid 

 , and glycerine, or cocoanut oil, attain a deep color in time, irre- 

 speetive of any animal matter in them. 



There was, however, another difficulty : a very fine cobra, 

 well hardened in spirit after some months, broke down from no 

 apparent cause. It was also found impossible to get a common 

 bloodsucker mounted in this medium. Neither gum and gly- 

 cerine nor strong spirit, nor arsenic paste, nor anything else 

 would keep them. In fact, the medium appeared either not to 

 be safe or not universally applicable. In order to study it and 

 learn what its action really was, I preserved a bloodsucker in 

 it direct, without previous preparation of any kind, and found 

 that I had a preservative of form as good as any known, and of 

 color as good as gum and glycerine itself. In this case the car- 

 bolic acid is either the dehydrator or, perhaps, combines with 

 the tissues and preserves them, whilst the oil acts as the atmos- 



