238 TAGG—NOTES ON MUSEUM-METHODS 
then congeals in shapeless masses on the surface of the fluid. On 
the other hand, the specimen removed from the preserving medium 
is in danger of drying, and a compromise has often to be made 
between the conflicting requirements of the cement and those 
of the specimen to be mounted. 
2. For heavy objects. 
Photoxylin will not support heavy specimens, so that resort is 
had in such cases to gelatine. It is extremely tenacious and 
will support specimens weighing several pounds if they are glued to 
the glass support at several points. In alcohol it becomes quite 
opaque, and its use is limited chiefly to those cases where the 
fastening cement is hidden behind the specimen. On a white 
background the cement, even if to a certain extent visible, is not 
conspicuous. On a black background its conspicuousness is 
~ lessened by mixing lamp black with it. 
The cement is prepared as follows :— 
Gelatine is soaked in water for several hours, the water not 
absorbed is then poured off and the gelatine heated over hot 
water. When melted, and of a fairly stiff consistency, it is ready 
for use. 
The specimen should be dried to a certain extent, all excess of 
alcohol removed, and the glass plate upon which it is to be mounted 
should be dry and warm. This last condition is secured by 
holding the glass for a second or two over a gas flame. The 
cement, used hot, is applied to the specimen, and the latter laid 
upon the mounting glass so that the cement comes in contact | 
with it and adheres to the warm surface. The cooling of the 
glass is hastened by running strong alcohol over the specimen 
_ from a pipette, which action serves the purpose also of preventing 
the specimen from drying. When the gelatine has cooled so as 
to be no longer in a fluid state, the glass plate with the specimen 
attached is placed in a bath of go per cent. alcohol. Itis left in 
this for the gelatine to harden by dehydration, the specimen lying 
horizontally and putting little strain upon the cement holding it. 
When quite hardened, the glass with the specimen is lifted out 
and is transferred tu the vessel in which the specimen is to be 
exhibited. 
To fasten with gelatine delicate specimens which would be 
