8o THE POPULAR SCIENCE MONTHLY. 



with, all its variations and fluctuations, stands in close relation to 

 the sum-total of heat of the earth's atmosphere. 



As, however, the warmth of the sun is influenced differently at 

 different places by clouds, by wind, and by damj^ness, it never reach- 

 es the organisms in its original condition. Notwithstanding this, 

 however, the fluctuations of weight-increase progress in harmony. 

 , Whatever it is that thus influences growth comes to us with 

 the speed of the sun's rays ; it varies from day to day, its intensity 

 is the same' at the same time throughout the globe, and it ,is not 

 subject to local causes, to changes by wind and by weather.^) 



Malling-Hansen calls this force " energy of growth " ; he sup- 

 poses that it reaches the earth with the speed of the heat-rays ; 

 separates from these, undergoes manifold changes, and, spreading 

 over the whole earth, is the cause of the uniform fluctuations in 

 the growth of all organic life. Upon future investigations falls 

 the burden of proof of this assumption. 



This influence of the sun-power may serve as an important 

 factor in testing systems of nourishment, in the arrangement of 

 diet-cures, and in studying the action of mineral waters. For in- 

 stance, what weight can be attached to an opinion formed on the 

 medicinal value of a mineral spring, if the test be made at a time 

 when the energy of growth is on the decrease, and is thus perhaps 

 assisting in the action of the spring, which at some other period 

 might prove itself only half as efficient ? 



Good nourishment, a limited amount of mental effort, and as 

 far as possible healthful surroundings during the maximum 

 period of growth of girth, may tend to re-establish the right pro- 

 portion of stature in children who have grown too rapidly. 



There is no known reason to doubt that adults gain and lose 

 in the same periods. If persons who are desirous of growing less 

 stout leave the watering-places at the end of August or earlier, 

 they do so at the time of weight-increase, and a careless diet will 

 hence, in shorter time than it would under similar circumstances 

 in winter, cause them to grow stouter again. 



With regard to the school vacations, these should be given 

 from the end of June to the beginning of September, during the 

 two maximum periods of growth ; the bodily strength which has 

 been gained will aid the mental work. — Translated for tJie Popular 

 Science Monthly from Dalieim. 



Prof. Gairdneb has called attention, in the British Medical Association, to the 

 need of medical students receiving more adequate instruction in physics. The 

 subordination of living bodies and physiological processes to all the most ele- 

 mentary laws of matter ; the correlation of all the physical forces ; and the medi- 

 cal methods involving applications of pure physics, combine to make this matter 

 an extremely important one. The physical laboratory will probably in a very few 

 years become an essential aid in the education of the physician. 



