NORMAL AND PATHOLOGICAL GROWTH 169 



tablished if the optimal physiological responses are to be at- 

 tained. 



Inactivity deprives the body of this stimulus to development. 

 Overactivity produces extreme fatigue and exhaustion for 

 which the compensatory reactions are inadequate. Metabolism is 

 not accelerated but is retarded. Positive injury results. Growth 

 is delayed and the body is stunted. The effects are more deeply 

 seated than a simple reversal of ledger balance between food 

 consumptions and growth, as against energy liberation and tissue 

 destruction. The overwork in some way injures the body proto- 

 plasm and the result is expressed in inertia, atonia, and retarded 

 metabolism. These extreme results are, of course, outside the 

 law that adjusted functional, that is, physiological activity, be- 

 gets energy, endurance, and growth. 



VIII. Pathological Tumors and Cancerous Growths 



There are numerous tissues throughout the body, especially 

 epidermal, muscular, glandular, and connective tissues, which 

 may run riot in growth, forming masses that are abnormal in 

 size and in function. These extra growths in turn produce 

 physiological substances not normal to the body but which may 

 be toxic and destructive. One may emphasize in these instances 

 the failure of inhibition or restraint of growth process to the 

 ordinary average level described as normal. 



The subject of abnormal growth and abnormal activity looms 

 large in the great field of pathological physiology. Perversions 

 of mass development and of the functional capacity may occur 

 in almost every part of the body and under an almost infinite 

 variety of conditions, many of which are quite unknown in 

 their causal relations. These growths and growth perversions 

 call for consideration, though the subject cannot be treated here 

 with any degree of thoroughness. 



In this field belong the great variety of special growths or tu- 

 mors, both benign and malignant. These structures are atypical 

 and abnormal, both from the standpoint of orderly growth of 



