NORMAL AND PATHOLOGICAL GROWTH 167 



data and the experimental data indicate that growth is influ- 

 enced by the two main divisions of the pituitary gland in very 

 distinctive ways. Furthermore, the influence of each gland is ex- 

 pressed in a twofold way — that produced by oversecretion, or 

 hyperactivity, and the condition induced by an undersecretion, 

 or hypoa'ctivity. There is not complete agreement among the 

 investigators of the pituitary, but, summarizing and combining 

 these sources of information, it would seem that the anterior 

 lobe in hyperactivity stimulates excessive growth in man and 

 lower animals. Rats grow to double their normal weight and 

 man to giant stature and giant weight. The muscular system of 

 animals and man is overdeveloped. The growth of the ovaries 

 is excessive and superovulation and the oestrus are facilitated. 

 Hypoactivity of the anterior lobe retards skeletal develop- 

 ment, the muscular system is small and weak, the development 

 of the nervous system is retarded, and mentality is subnormal. 

 Metabolism is definitely reduced and the temperature is lower 

 than normal. In the posterior lobe an increase in activity aug- 

 ments sugar metabolism, stimulates the contractions of smooth 

 muscle in the intestine, reproductive system, and blood vessels, 

 and produces hyperirritability. A deficient posterior secretion 

 is characterized by decreased oxidation, increased volume of 

 urine, carbohydrate tolerance with excessive fat production, 

 nervous or mental indolence and inactivity, abnormal body 

 form, and infantilism. 



VII. The Influence of Physiological Exercise on Growth 



A further important physiological point of view was ex- 

 pressed by Dr. Robbins in the introductory lecture of this series, 

 namely, that growth processes are inseparable from dynamic 

 processes. Energy liberation is ever accompanied by destruction 

 and repair of body tissue. Growth in animals is not a simple ac- 

 cumulation of a mass of stored materials, it is the formation of 

 a mass of intimately organized and highly differentiated living 

 protoplasm of corresponding complex physiological capacity. A 



