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CHAPTER XI.
BRAIN AND NERVES.
On account of the difficulty in making a mechanical separation
and isolation of the different tissue-elements of the central nervous
organ and the nerves, we must resort to a few microchemical reactions,
pr ncipally to qualitative and quantitative investigations of the different
parts of the brain, in order to study the varied chemical composition
of the cells and the nerve-axes. This study is accompanied with the
greatest difficulty, and although our knowledge of the chemical com-
position of the brain and nerves has been somewhat extended by the
investigations of modern times, still it must be admitted that this sub-
ject is as yet one of the most obscure and complicated in physiological
chemistry.
Proteins of different kinds have been shown to be chemical constit-
uents of the brain and nerves, and these are representatives of the same
chief groups as occur in the protoplasm. In the brain there occur some
proteins which are insoluble in water and neutral salt solutions, and
which resemble the stroma substances of the muscles and cells, while
other proteins are soluble in water and neutral salt solutions. Among
the latter we find mainly nucleoproteins and globulins. The nucleo-
protein found by Halliburton and also by Levene 1
in the gray substance
contains 0.5 per cent phosphorus and coagulates as 55-60°. Levene
obtained adenine and guanine but no hypoxanthine as cleavage prod-
ucts. According to Halliburton there are two globulins, namely,
the neuroglobulin a, which coagulates at 47°, or as in the case of
birds, 50-53°, and the neuroglobulin /3, whose coagulation temperature
is 70-75°, but which varies somewhat in different animals. In the frog
still another protein body occurs, which coagulates at a still lower tem-
perature, about 40°. It must be remarked that the coagulation tempera-
ture of a-globulin corresponds with the temperature of the first heat
contraction of the nerves of different classes of animals (Halliburton).
1
Halliburton, On the Chemical Physiology of the Animal’s Cell, King’s College,
London, Physiological Laboratory, Collected Papers No. 1, 1S93, and Ergebnisse der
Phyeiologie, 4; Levene, Arch, of Neurology and Psychopathology, 2 (1899).
604
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