June, 1913. 



KNOWLEDGE. 



209 



realm of male and female is thus shown. The side 

 corresponding with the opposite sex. i.e., the left, is 

 accentuated more strongly. "Accentuated " does 

 not imply by any means that the person in question 

 is always undoubtedly left-handed. This is as 

 problematic as it is interesting. 



Broca's sensational discovery that the centre of 

 speech in the human brain is situated on the left 

 side, which was confirmed and extended by Bastian's 

 painstaking investigations, was all the more a matter 

 for wonder as the examination of animals gifted with 

 a certain power of speech manifested no such one- 

 sidedness. It was established that this one-sidedness 

 in man was connected with his right-handedness. 

 Further research showed that in the case of the left- 

 handed the centre of speech was situated in the right 

 cerebral hemisphere. There was, therefore, no 

 longer any doubt as to the interdependence between 

 the left position of the speech centre and right- 

 handedness. Already in the seventh and eighth 

 centuries scientific men were aware that diseases of 

 the left cerebral hemisphere were very often attended 

 by difficulties in speech, whereas this was extremely 

 rare — only with the left-handed — in cases of disease 

 of the right half of the brain. This, too, confirms 

 Broca's discovery. A right-handed person may 

 suffer loss of speech through a blow on the left side 

 of the head, and a left-handed person by a blow on 

 the right side. 



Consequently, people whose two hands are equally 

 skilful should have two speech centres. This seems 

 actually to be the case. Dr. Ernst Weber says that 

 it is easy to detect in children unmistakable traces 

 of two speech centres, but that later one of the 

 centres atrophies owing to the preference given to 

 one hand. But though it atrophies, it can be 

 aroused again and rendered useful by systematic 

 development of the other hand. How very far this 

 resuscitation can be made to go is shown in practice 

 by numerous successful experiments in trying to 

 make people ambidextrous by way of training the 

 left side. Of course, these experiences tend to 

 disprove Dr. Lueddeckens' utter disbelief in 

 gradually acquired habit as a possible cause of the 

 prevalence of right-handedness. 



With regard to the number of cases of left- 

 handedness, Hasse and Dehner estimate it at one 

 per cent., many others at from two to four and a 

 half per cent., Flechsig at three per cent., and 

 Biervliet at two and a half per cent. The Bible 

 states that in the tribe of Benjamin, which 

 numbered twenty-six thousand seven hundred men, 

 there were seven hundred left-handed ; this would 

 be 2-62 per cent. Up to the present no one has 

 been able to draw up far-reaching statistics referring 

 to thousands of cases — and such alone would be 

 really reliable — as no investigator has examined and 

 compared more than a few hundred. 



EFFECT OF SCHOOL WORK ON THE LUNGS. 

 By DR. ALFRED GRADENWITZ. 



Interesting experiments have recently been made 

 by Dr. M. Oker-Blom, of Helsingfors, on the 

 respiratory movements on both sides of the chest of 

 twenty-five school children in the course of different 

 kinds of work, by means of an apparatus recording 

 any variations in these movements.* When reading 

 aloud was practised for three minutes, the upper 

 parts of the left lung were found to breathe more 

 deeply than those of the right lung, irrespective of 

 whether the pupil was seated or standing, the ratio 

 of the respiratory movements on the right and left 

 sides respectively being r : I = 100 : 118. This is, 

 of course, an average figure, there being sometimes 

 exceptions, especially in cases where the left lung is 

 somewhat abnormal. 



The total number of respirations (r -\- I) on both 

 sides together during reading aloud is on an average 

 seventy-eight when the pupil is standing, but 

 decreases to seventy-two if he is sitting. 



The most important point brought out by these 

 experiments, however, is the influence exerted by a 

 prolonged sitting posture on the respiration of the 

 upper part of the lungs. During a sedentary occu- 

 pation of some duration {e.g., knitting) the two sides 

 of the chest are found generally to have the same 

 amplitude of respiration, the breathing movements 

 of the left side being impeded more than those of 



the right. This is accounted for by the frequent 

 changes in the position of the body which are made 

 involuntarily from time to time to alleviate the 

 fatigue in the back. In fact, even in cases where 

 there is no habitual scoliosis, the vertical column is 

 found alternately to lean to one side or the other, 

 the body straightening itself from time to time, 

 while a few deeper respirations ensure a certain 

 amount of compensation. In any case the unfavour- 

 able influence of any prolonged sedentary occupa- 

 tion generally is more marked in its effects on 

 respiration in the upper parts of the left side than 

 in those of the right. The total number of respira- 

 tions is found to decrease during uninterrupted 

 sedentary work lasting up to about forty minutes, 

 from seventy-two to thirty-nine, i.e., to about half 

 its original value. This is accounted for by the fact 

 that during sedentary work certain groups of 

 muscles are extended without interruption, thus 

 impeding the freedom of respiratory movements. 



In order to obviate the harmful action of prolonged 

 sedentary work it is recommended that such work 

 should be from time to time interrupted by a few 

 minutes' respiratory gymnastics. Not only would 

 such practice prove beneficial as regards respiration 

 and pulmonary exercise, but it would, in addition, 

 have a certain prophylactic effect against scoliosis. 



Internat. Archiv f. Schulliygiene, 



