EXCITATION AND CONDUCTION 79 
of carbon dioxide of two equal weights of proximal and 
distal portions of the same nerve were compared in the 
biometer under identical conditions. The portion of 
the nerve which gave off sufficient carbon dioxide to 
produce the precipitate of barium carbonate in the 
shortest time and the greatest abundance evidently 
produced the most carbon dioxide. 
TABLE XIII 
CoMPARATIVE STUDIES ON RATE OF CARBON DIOXIDE PRODUCTION FROM Two 
PorTIONS OF VARIOUS NERVES 
TEMPERA- 
TURE OF NERVE AMOUNTS 
DatTE Room oF CO. 
é DEGREES COMPARED 
G. Name of Kind of | Portion of | Weight of 
Aug. 31... 23.2 Optic nerve of | Afferent |{Proximal 17 mg.| Less 
Limulus mainly |\Distal 17 More 
Sept. 15... 18 Optic nerve of Proximal 23 Less 
skate et Distal 23 More 
Feb. 15... 22 R. lat. vagi of Proximal 4.4 Less 
carp a Distal 4 More 
Dec. 20... 20 R. lat. vagi of Proximal 2 Less 
catfish £ Distal 1.8 More 
Dec. 13... 17 R. lat. acc. of Proximal 1.4 Less 
catfish f Distal 1.4 More 
Nov. 23... 25.5 Posterior root Proximal 6.5 Less 
of dog - Distal 6 More 
Aug. 30... 21.8 Claw nerve of | Efferent | {Proximal 32 More 
spider crab mainly |\Distal 44 Less 
Feb. 26... 19 Hypoglossal Proximal |\Equal More 
nerve of dog & Distal weights | Less 
Feb. 21... 23 Same nerve of Proximal |\Equal More 
carp * Distal weights | Less 
Sept. 15... 17.8 Oculomotor Proximal II More 
nerve of skate e Distal II Less 
Nov. 26... 26 Anterior root Proximal 1.6 More 
of dog - Distal 1.8 Less 
While we have not by any means exhausted the 
various kinds of nerve fibers available for the study 
of this gradient, the results obtained in those nerves 
already examined have been very uniform and the 
nerves themselves have had varied functions and have 
come from several different classes of animals, namely, 
