2 6o THE POPULAR SCIENCE MONTHLY
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 influ- ence 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 in- creased 29 out of 33 times. The author holds that the study " dis- tinctly " 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 determin- ing the total condition: (a) the difficulty of the school work; (&) the length of the work period; (c) the frequency of the recitation inter- vals; (d) the amount of exercise and the access to fresh air.
Arduous mental work produces destructive changes in the blood, while re- cuperation causes the elimination of waste products and finally a more or less active regeneration of corpuscles.
Observation of the children also showed that external manifestations of fatigue invariably accompany the microscopical phenomena associ- ated 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.
While a considerable degree of disintegration could be noted in the morning after several weeks of concentrated sedentary work indoors, accompanied by physical depression, lassitude and heaviness, this phenomenon disappeared, to- gether with the subjective symptoms, after a walk of two hours. On another occasion the disintegration quotient increased considerably after four hours in- cessant work at the microscope prior to taking food and following a prolonged period of close application to research work, but decreased rapidly after two hours devotion to a totally different occupation and lunch taken in the open air.
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,