GENERAL ARRANGEMENT OF ITS CONTENTS. 
19 
logical time: distinctions which, in most cases, can only be 
appreciated when the specimens exhibiting them are kept under 
such conditions as to admit of ready and close examination and 
comparison. It is to this part of the collection that zoologists 
and botanists resort to compare and name the animals and plants 
collected in expeditions sent to explore unknown lands, to work 
out biological problems of the highest scientific importance, and 
generally to advance the knowledge of the science. In fact 
these reserve collections, occupying comparatively little room, 
kept up at comparatively little cost, and visited by compara- 
tively few persons, constitute, from a scientific point of view, 
the most important part of the Museum, for by their means new 
knowledge is obtained, which, given forth to the world in the 
form of memoirs, books, or lectures, is ultimately diffused over 
a far wider area than that influenced even by the exhibited 
portions of the Museum. Indeed, without the means of study 
they afford, the order, arrangement, and power of imparting 
knowledge, which the exhibition galleries possess, would not 
be possible. 
It is important to bear in mind that if the whole of such 
specimens as are really required for enlarging the boundaries 
of knowledge were displayed in the public galleries, so that each 
one could be distinctly seen, a museum very many times larger 
than the present one would not suffice to contain them; the 
specimens themselves would be quite inaccessible to the exami- 
nation of all those capable of deriving instruction from them, and 
owing to the disastrous effects of exposure to light upon the 
greater number of preserved natural objects, would ultimately 
lose almost everything that now gives them value. This portion 
of the collection must, in fact, be treated as are the books in a 
library, and only used for consultation and reference by duly 
accredited students.* 
In some parts of the Museum the reserve collections are con- 
tained in drawers beneath the cases in which the corresponding 
exhibited portion is placed. This applies principally to the 
pala3ontological specimens, the shells, and the minerals. The 
reserve birds and insects have special rooms devoted to tliem, 
* For conditions as to admission and reuulation, see p. GG. 
c 2 
