XX 
The Mammals of Colorado 
Skins treated in the above manner can be easily softened 
and turned and made up into museum skins at leisure, but 
it is of course best to do this on the spot if one knows how, 
and has the opportunity. 
While this book has been in the printer's hands Professor T. D. 
A. Cockerell of the University of Colorado has written me concern- 
ing some investigations made by one of his students upon the anat- 
omy of certain genera, and which show some interesting differences 
in the relative lengths of the large and small intestines. In Crato- 
geomys the large intestine was always the longer, and the reverse 
the case in Perodipus. Other similar facts were found in Peromys- 
cus b. rowleyi, Onychomys I. pallescens, and Thomomys agrestis. 
These investigations were made upon material saved by myself 
during the past season in various collecting trips, and was mostly 
the carcasses of specimens which I had skinned, and which I had 
preserved in alcohol at Professor Cockerell's request, and which 
would otherwise have been thrown away. 
I mention this in this connection because it shows there is a 
field for original work upon the anatomy of our mammals, and the 
material is easily obtained by saving the bodies of such specimens 
as are skinned, or the whole animal if the skin is not desired. Speci- 
mens for this purpose can be preserved in alcohol, either common 
or denatured; ten to twenty per cent, of water should be added 
to the alcohol; or formaldehyde may be used instead of alcohol, 
using one part of formaldehyde as sold in the drug-stores to ten or 
fifteen parts of water. Glass preserve jars are just the thing for 
holding the specimens. Whole unskinned specimens should have 
a short cut made in the skin of the belly to admit the preservative. 
Each specimen should have a label stating what it is, and other 
necessary data, and this should be written in pencil, or some form 
of India ink. Any of Higgins' black inks are good. But never use 
common writing ink on a label which is to go into alcohol or formalde- 
hyde as the writing is almost certain to be obliterated. Always use 
heavy writing paper for the label, never a cardboard label, that 
goes to pieces when wet. If the specimens are to be transported 
far it is well to wrap each in a piece of cheese-cloth or something of 
the sort to prevent too much rubbing together and destruction of 
labels. If collectors will do this and turn the material over to 
interested persons they will aid much in advancing our knowledge 
concerning our mammals, and at but little trouble to themselves. 
