458 SIMON H. GAGE 
GLYCOGEN IN THE NERVOUS SYSTEM OF MAMMALS 
Sus scrofa. The pig was selected for determining the pres- 
ence of glycogen in the nervous system of mammals because of 
the abundance of material obtainable at all periods of develop- 
ment. Other mammals were examined as opportunity offered, 
and it was found that whatever occurred in the pig appeared 
also in other mammals if taken at the favorable developmental 
state. 
Up to the present, glycogen has been found by me in the cells 
of the dorsal root ganglia of pigs up to a length 15 mm., those of 
10 to 12 mm. in length had perhaps the greatest number of nerve 
cells with the glycogen. At this time the outgrowing nerves 
seem to be wholly free from glycogen, but commencing with 
embryos of 30 mm. and as large as 70 mm. and perhaps older 
ones, the nerves within and beyond the ganglion are so filled 
with glycogen that they appear a deep brown. 
In addition to the nervous element proper, the endymal cells 
of the relatively free choroid plexus are filled with it in the 
older embryos, 1.e., those of 40 to 70 mm. and perhaps older ones. 
In addition to the cells on the free plexus, those extending for a 
considerable distance upon the ventricular wall are well supplied 
with glycogen. 
In the fourth ventricle the endymal cells contain glycogen 
at a somewhat later stage, viz., in embryos of 50 to 75 mm. in 
length. 
Abundant glycogen was also found in the olfactory as well 
as the respiratory epithelium of the nose; and its presence is 
very marked in the epithelium of the cochlear canal opposite the 
organ of Corti. The eye has not yet been sufficiently studied, 
but the appearance of glycogen at some period is predicted. 
Glycogen was found in every organ and tissue in the body of pig 
embryos at some period of development. Naturally the heart 
contained much of it. For example, in the smaller pigs studied, 
i.e., those of 8 to 16 mm., the cardiac glycogen was so abundant 
that it made the heart sections almost opaque. In embryos of 
70 mm. the amount was relatively less. The liver contained no 
