Page:Popular Science Monthly Volume 84.djvu/263

Rh could hardly fail to affect unfavorably that organ most concerned in the overpressure—the brain itself.

Binet and Schuyten (2), by carefully weighing the quantities of food consumed by school children in the different months of the school year have been able to show that the child's appetite deteriorates as the school year proceeds. The exact causes of such deterioration are very complex and difficult to disentangle, but the basis, at least, for an explanation is to be found in such investigations as those of W. B. Cannon, Pavlow and others on the physiology of digestion.

Data of this kind lead us to infer that the nervous stimulation involved in excessive mental work produces its injury through such reflex effects as those upon the nutritive processes. Graziani, however, has raised the question whether in addition there may not be unfavorable influences more direct than this explanation assumes. He believes there are two such influences: (a) Imperfect oxygenation of the blood and incomplete elimination of carbon dioxide due to the superficial respiration proved by Mosso, Macdonald, Bush, Obici and others to result from application to mental tasks; and (b) an immediate effect upon the chemical composition of the blood corpuscles due to the accumulation of fatigue products resulting from mental work (5).

In order to test the latter theory, Graziani subjected 18 university students and 17 children of ten to twelve years of age to blood tests before and after the preparatory period for school examinations. The tests involved three determinations: the number of red corpuscles, the relative proportion of hemoglobin which they contained, and their power of resistance. In regard to the number of corpuscles, no constant differences were found either with university students or with children. The proportion of hemoglobin, however, showed a decided decrease, amounting to an average of 10 per cent, with the students and to nearly that much with the children. The effect upon the power of resistance of the red corpuscles was much the same as other investigators had shown to result from certain poisons. Graziani, therefore, concludes that in all probability mental work produces a toxin which brings about an immediate change in the chemical and functional properties of the blood.

To try this theory still further he subjected himself and a twelve-year-old boy to the same kind of blood examinations, except that in this experiment the blood tests were separated only by a number of hours of strenuous mental work instead of by many weeks, as was the case in the earlier experiment. Here, again, the decrease of homoglobin was marked, amounting on an average to 7.5 per cent, with Graziani himself and to 8 per cent, with the boy. Graziani believes that the underlying cause of school anemia, with its alterations of metabolism and its imperfect oxygenation of the blood, is to be sought in the influence of excessive accumulations of toxic products of fatigue.