A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . vousmetabolism. It islikely, therefore, thatalthough the changesin temperature areeasily determinable,these changes are dueto something otherthan the oxidation ofcerebral tissue, andthat there is no greatamount of heat pro-duced in or by thenerve tissues duringmental activity. Thevariations in bloodsupply which accom-pany cerebral activ-ity are sufficient toexplain the temper-ature changes, andthese are probably the determining factors. By mostcareful experiments o
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . vousmetabolism. It islikely, therefore, thatalthough the changesin temperature areeasily determinable,these changes are dueto something otherthan the oxidation ofcerebral tissue, andthat there is no greatamount of heat pro-duced in or by thenerve tissues duringmental activity. Thevariations in bloodsupply which accom-pany cerebral activ-ity are sufficient toexplain the temper-ature changes, andthese are probably the determining factors. By mostcareful experiments on nerves, Helmholtz and otherswere unable to find any changes in temperature, andit may be concluded that the results of all experi-ments indicate that nervous activity in itseff does notappreciably alter the temperature of the brain orother parts of the nervous system. Chemistry of the Brain.—.although the chemicalanalysis of brain tissue has not furnished any infor-mation regarding cerebral function, the facts are ofinterest, and possibly will have greater importancewhen this topic is more frequently made the subject 401. Fig. 1036.—Latent Periods of Move-ment Following Excitation of {M)Cerebral Cortex, and of (.V) Subja-cent Corona Radiata in the Dog. Ineach set of curves upper line givesmovement, middle line time intervalsin second, and the lower line thetime of stimulation. (From Schafer,after Franyois-Franck and Pitres.) Brain, Physiology of REFERENCE HANDBOOK OF THE MEDICAL SCIENCES of investigations by physiological chemists. Themost important investigations have been those ofThudicum, who differentiated numerous complexsubstances, of most of which the exact compositionsare stiU open to question. The watery content of the brain is large, that of thewhole being about seventy-six percent., of the cortexabout eight3-three per cent., and of the white matterabout seventy per cent. (Koch). In the young childmore water is found, being about eighty-eight percent, of th
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