1086 The American Naturalist. [November, 
PHYSIOLOGY. 
Temperature in Nerves.—Rolleston,! by using an electrical 
resistance thermometer sufficiently delicate to appreciate one five- 
thousandth of a degree, finds, like other investigators, no evidence of 
the evolution of any heat from the nerve during the passage of a 
nervous impulse. In dying a nerve evolves heat, in some cases one- 
seventh of a degree C. The frog's sciatic was chiefly used. 
Neurokeratin.— This substance, characterized by extreme insolubil- 
ity, was discovered by Ewald and Kühne, in 1877, in medullated nerves 
and the central nerve substance. Kühne and Chittenden? have su 
jected it to a careful study. The nerve tissue was freed from the 
myelines by prolonged treatment with alcohol and ether ; from all di- 
gestible matters by gastric and pancreatic juices ; and from nuclein by 
extraction with alkali. Analyses of neurokeratin thus obtained from 
human brains gave C 56.11 to 58.45, H 7.26 to 8.02, N 11.46 to 
14.32, S 1.63 to 2.24. Noticeable are the absence of P and the low 
amount of S. Cis somewhat higher and N somewhat lower than in 
albuminous bodies. Ordinary keratin from rabbit's hair gave C 49.45, 
H 6.52, N 16.81, S 4.02, in which S is double its quantity in neuro- 
keratin. The nerve cord of the lobster, treated in a similar manner, 
yielded a residue of chitin with no neurokeratin. Quantitative deter- 
minations in man gave for peripheral nerves . 316 per cent., for cortex 
of cerebellum .312 per cent., for cortex of cerebrum . 327 per cent., 
and for white substance of the corpus callosum 2.902 per cent. The 
results indicate for myeline-free, dry nerve substance, 1.91 per cent, 
of neurokeratin ; do. gray substance, 3.22 per cent. ; do. white sub- 
stance, 33.77 per cent. Methods are given by the authors whereby 
this substance may be detected in nerve fibres. 
Sensitiveness of Joints.—In studying the muscle sense Goldschei- 
der hypothecates for the joints the two functions of mediating sensations 
of movement and sensations of resistance. For the former the sensi- 
tive substratum is to be found doubtless in the nerves and nerve end- 
ings of the capsule of the joint, these being stimulated by the working 
of the joint. For the latter the question arises whether in the | 
Surfaces the supposed sensitiveness really exists. He tests this® 
1 Journal of Physiology, Vol. XL, 1890, p. 208. 
3 Zeitschrift f. Biologie, Ba. XXVI. ; also N. Y. Medical Journal, 1890. 
m d. Berl. Physiol. Gesellschaft ; in Du Bois Reymond’s Archiv, 1890, P. 
