Page:Popular Science Monthly Volume 84.djvu/264

260 Another important study of this type by Helwig (6) corroborates the findings of Graziani. This author made many blood tests upon himself and six other subjects for the purpose of determining the influence of school work, fresh air, rest, marches and lessons of different degrees of difficulty both upon the number of red corpuscles and upon their "degenerative" and "regenerative" processes. The study seems to have been made with the most approved technique and with the greatest regard for scientific accuracy.

The results were rather variable for the corpuscle count, but quite striking as regards the "degenerative" and "regenerative" processes.

As a result of school work the "disintegration-quotient" was increased 29 out of 33 times. The author holds that the study "distinctly" demonstrates that school work not only imposes a strain upon the nervous system, but that it produces a "destructive effect on the blood corpuscles." The numerous tables presented by the author show rather convincingly the influence of the following factors in determining the total condition: (a) the difficulty of the school work; (b) the length of the work period; (c) the frequency of the recitation intervals; (d) the amount of exercise and the access to fresh air.

Observation of the children also showed that external manifestations of fatigue invariably accompany the microscopical phenomena associated with this state.

It was not only from highly sensitive children that these reactions were obtained. The author observed the same phenomena in his own person after long-continued mental strain.

Rest days showed an immediate effect in a lower disintegration quotient. Long and tiring marches produced only small degenerative values and were followed by rapid regeneration. During a day of mental work disintegration continually increases until late in the afternoon, indicating that this part of the day is least suitable for hard study.

The reverse phenomenon, the improvement which takes place in the composition of the blood as the result of a well-spent summer vacation,