CHAPTER XII. 

 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, 

 chiefly 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 composition 

 of the brain and nerves has been somewhat extended by the investiga- 

 tions of modern times, still it must be admitted that this subject 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 chiefly nudeoproteins and globulins. The nucleo- 

 protein found by HALLIBURTON and also by LEVENE * in the gray substance 

 contains 0.5 per cent phosphorus and coagulates at 55-60. LEVENE 

 obtained adenine and guanine but no hypoxanthine as cleavage 

 products. According to HALLIBURTON there are two globulins, namely, 

 the neuroglobulin a, which coagulates at 47, or at, in the case of 

 birds. 50-53 and the neuroglobulin /?, 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). 



There does not seem to be any doubt that the proteins chiefly belong 

 to the gray substance of the brain and to the axis-cylinders. The same 



Halliburton, On the Chemical Physiology of the Animal's Cell, King's College, 

 London, Physiological Laboratory, Collected Papers No. 1, 1893, and Ergebnisse der 

 Physiologic, 4; Levene, Arch, of Neurology and Psychopathology, 2 (1899). 



574 



