11 
the “arsenic-and-alum” mixture has been more or less replaced by 
“arsenic and borax” for ordinary collecting purposes, the alum recipe is 
very useful in some cases. 
The field collectors for the American Museum of Natural History, 
New York, who have done much work in the humid parts of South 
America, Asia, and central Africa, have generally adhered to the use of 
white arsenic (arsenic trioxide) or arsenic and alum in equal parts by 
volume (Chapin, 1923, page 6), but Mr. Chapin informed me in 1930 
that he had recently been substituting borax for the alum almost exclu- 
sively. Alum has the disadvantage of hardening the skin somewhat, but a 
mixture of arsenic and alum may be very useful for very large birds in 
hot, moist climates. Chapin states that the arsenic is used for its permanent 
effect in preventing insects from eating the skin, rather than for any 
immediate action as a preservative, and that the arsenic should never be 
omitted. Anthony (1925, page 8) states that the skins of small mammals 
are best preserved by a mixture of arsenic and powdered alum (ammonium) 
the proportion about half and half by volume or by weight. Mr. Herbert 
Lang, who has had many years of experience in collecting mammals and 
birds in Africa, states that arsenic was necessary to prevent the attacks 
of insect pests, and advocates increasing the proportion of alum where the 
climate is very hot and moist. 
Alum has an astringent or shrinking effect which is considered more 
or less detrimental to skins that are to be mounted later. The fur of 
certain species, as hair seals and squirrels with fur of certain shades of 
brown or yellow, are apt to have the colour of the hair changed to a deep 
yellow colour by either salt or alum, and the old-fashioned salt-and-alum 
bath for skins has largely gone out of use for that reason. Mr. A. H. Howell 
(1937, page 95) deprecates the use of salt and alum as it causes specimens 
to become noticeably altered in colour, and Professor E. Raymond Hall 
(1937, pages 359-360) warns against the method of salt and alum curing, 
stating that specimens of chipmunks, kangaroo rats, black bears, and mule 
deer may have colour of coat badly altered by its use. He states that if the 
salt-alum treatment is used, the least that should be done is to label the 
skins to clearly indicate departures from the conventional technique. 
The small amount of alum used in touching up uncured spots will 
hardly be sufficient to affect the colour of the hair, but it may be well to 
attach a tag stating where alum has been used on the skin, so it can be 
scraped off before the skin is placed in the tanning solution. 
The experience of the writer is that in the temperate parts of North 
America (including all of Canada) the use of alum is ordinarily unneces- 
sary in curing specimens, and on account of its shrinking and hardening 
properties it is unsatisfactory for general use. However, alum is a very 
important agent for certain emergencies, and the field collector should 
always have a little on hand. In some cases when a valuable specimen 
has remained too long without being skinned, with the hair or feathers 
loose and about ready to slip off, a little alum in the preservative will 
“set” the hair and feather roots until the skin is dry. Sometimes in warm 
weather a mammal that is pretty far gone, with the skin turning green 
on the under parts, may be saved by quickly removing the skin and soaking 
it in a hot (but not scalding hot) solution. A little alum may be mixed 
with the fine sawdust that is used as an absorbent while skinning such a 
