462 SIMON H. GAGE 
as in balsam mounting. As the vaseline does not hold the cover very 
firmly, it is best to seal the cover with shellac. . 
Specimens so stained may be restained at any time by reversing the 
process and then remounting. The stain remains for two to ten years. 
A second method was to mount in Canada balsam without a cover- 
glass, as with the Golgi preparations. For this dried balsam is pow- 
dered and to 25 grams of dry balsam, 50 ec. of xylene is added. The 
sections are deparaffined, and the balsam put over them and allowed 
to dry in the air. More than one coat of balsam may be needed. 
The glycogen stain is not so persistent in the balsam, but for high 
power work the finest details are more satisfactory. If a homogeneous 
immersion objective is to be used the original immersion liquid, viz., 
Canada balsam of moderate thickness is better than cedar oil. It 
need not be removed. The other stains recommended for glycogen 
are not so precise as iodin, and are lable, if not checked by iodin, to 
lead the investigator astray. 
The most exact test for glycogen is saliva. If a section is deparaf- 
fined, washed off with alcohol and water, and then saliva put upon 
it for half an hour, if the substance is glycogen it will be changed to 
sugar by the enzyme of the saliva. If now the section is restained 
with iodin no mahogany red glycogen will appear. This test was | 
applied to all the work given in the accompanying paper to make 
sure that the reddish brown substance in the cells was glycogen and 
not something else. 
BIBLIOGRAPHY 
The literature of glycogen is very extensive, and may be found in the Index 
Catalogue of the Library of the Surgeon General’s Office, Ser. I, II, and in 
special papers such as Fichera’s with its 311 references and in Pfliiger’s book on 
Glycogen. Only the works bearing directly upon the subject of this discussion 
are here given. 
BarrurtH, D. 1885 Vergleichend-histochemische Untersuchungen iiber das 
Glycogen. Arch. f. mikr. Anat., Bd. 25, pp. 261-404. Nervous sys- 
tem of vertebrates, pp. 297, 299. Invertebrates, p. 298. While deny- 
ing glycogen to vertebrate nervous tissue at any period, p. 299, he 
reported its presence in small amounts in the nervous system of 
snails. 
BerNarp, CLaupr 1859 De la matiére glycogéne considerée comme condition 
de développement de certain tissus chez le foetus avant l’apparition 
de la fonetion glycogénique du foie. Jour. de la Physiol. t. 2, Pp. 
326-337. 
1878-1879 Legons sur les phénoménes de la vie communs aux animaux 
et aux végétaux. Two volumes. 
3ernard wrote many papers upon sugar in the blood and upon gly- 
cogen, which he discovered and isolated in 1857. The paper cited 
above and the volumes on the phenomena of life give his views very 
