EQUIPMENT, ARMS, AND SPECIMENS 747 
desirable are the skulls of specimens with really large tusks 
which would show the changes of bone structure which ac¬ 
company gigantic tusk development. The largest skulls at 
present preserved in museums possess tusks of considerably 
less than two hundred pounds per pair, which are less than 
half the weight of record tusks. It is well to bear in mind 
that our large mammals are disappearing more rapidly than 
the smaller ones, and in the districts where they are now 
rare special efforts should be made to obtain and preserve 
specimens before their extinction. In order to determine 
the characters of the geographical races of a species it is 
necessary to have specimens for study from every district 
inhabited by the species. Game reserves can only protect 
or preserve species in certain limited areas, and we cannot 
therefore possibly preserve by such means all the geograph¬ 
ical races of widely distributed species. To carry out such 
complete preservation would require the protection of all 
the species of game animals throughout their entire ranges, 
which is obviously impossible. It should be our especial 
purpose to obtain specimens of the species which are disap¬ 
pearing most rapidly, in those districts where they are 
already rarest. 
The salt method of preservation here described is essen¬ 
tially that of Carl E. Akeley, and was the one employed by 
the Smithsonian African expedition under the direction of 
Colonel Roosevelt. Owing to the great quantities of salt re¬ 
quired both in dry-salting the skins in the field and later in 
packing them in barrels for shipment, it is a very expensive 
process. To the cost of the salt must be added the much 
greater cost of transportation of the skins in the field 
due to the added weight of salt. It has great advan- 
