SHEA — A8PECT8 OF MENTAL ECONOMY. 185 



fective vision, and from too concentrated employment of the 

 eyes. Before leaving this general topic, a word should be said 

 regarding another factor in the causation of wasteful tensions. 

 The human body in a standing or sitting position is, as every- 

 body knows, acted upon by gravity, and if it be thrown out 

 of plumb, so to speak, it tends to fall to the earth. This catas- 

 trophe can be averted only by the action of muscles which pull 

 against gravity, and so serve to keep the body in equilibrium. 

 Suppose now a person on foot or in his seat in such a posture for 

 some time that gravity has a leverage on him, and his muscles 

 are doing their best to prevent his falling ; it is easy to see what 

 this means in terms of nerve force. It involves nothing less con- 

 sequential than a ceaseless drain upon the system. People who 

 do not habitually stand or sit in such manner that the body is 

 poised, as it were, and at rest, will certainly suffer for their 

 error in lessened efficiency in both physical and mental work. 



This principle is of special value to a student as it relates 

 to the position he habitually takes while engaged in study. In 

 order that this position may comply with the requirements of 

 economy in the expenditure of nervous energy, the study desk 

 and chair must be exactly adjusted to the bodily measurements 

 of the individual so that while using them there may be little oc- 

 casion for muscular strain. !No statistics have been gained re- 

 garding local conditions in respect of this matter, since in order 

 to be of value they would require considerable exact measure- 

 ment and this we could probably not have secured ; but it is not 

 unreasonable to suppose that students have not accidentally and 

 in all cases hit upon the proper regulations respecting the height 

 of desk and chair and their "distance" relations to each other. 

 Now, recent investigation has established something like a law 

 of hygienic seating Lincoln, 1 Barnard, 2 Marble, 3 and others 

 in our own country and many scientists abroad 4 have given much 

 attention to this subject during the past few years, alike in the 

 study of the physiological conditions which should govern seat- 



i The Sanitary Conditions and Necessities of School-houses and School Life. 



'School Architecture, New York, 1860. 



3 Sanitary Conditions for School-houses. 



4 See The Pedagogical Seminary, June, 1892, for a summary of investigations. 



