

FRANCIS H. McCRUDDEN 



BOSTON 



Introduction 



We can imagine two fundamental causes for failure of an animal to 

 grow: (1) Absence of the capacity to grow; (2) absence of available 

 structural material. Dwarfism occurs as the result of disease or removal 

 of the thyroid or thymus, for example, even when the food supply is 

 abundant. The capacity to grow, in this case, is missing. Failure to 

 grow is not seen as the result of complete starvation ; death ensues too 

 soon for this. But partial starvation, the result of a diet rich enough in 

 caloric value and complete enough for the bare maintenance of a young 

 animal, but lacking certain essentials for growth may lead to dwarfism 

 from the lack of material for growth. Both of these forms of dwarfism 

 have been studied experimentally, and the results are fully discussed else- 

 where in these volumes. 



A scientific study of infantilism should, if possible, present the subject 

 from the point of view suggested in the preceding paragraph. But the 

 metabolism in different types of dwarfism has been so little studied that 

 in many cases it is not yet possible to determine which of the two funda- 

 mental causes is responsible. Nearly every writer who discusses infantil- 

 ism presents a classification of his own. All investigators agree that three 

 forms of the disease are easily recognizable: cretinism, achondroplasia, 

 and mongolianism. Besides these, every writer on the subject describes 

 cases of infantilism which do not appear to belong to any one of these 

 three groups ; in many cases the supposed etiology is given. Thus cases 

 of infantilism have been described as due to disease of the liver, pancreas, 

 heart, lymphatic system, cerebral tumor; others as due to tuberculosis, 

 chlorosis, pellagra ; and still others as due to poisoning from alcohol, lead, 

 or mercury, or to a generally poor hygienic environment. 



Those who have been making scientific studies of nutrition and growth 

 in animals have generally refrained from attempts to apply their results 

 to the explanation of any of the recognized forms of spontaneous dwarfism 

 occurring in man. And writers on infantilism in man have generally re- 

 stricted themselves to clinical descriptions of the forms of infantilism they 

 have observed, comparing their cases with other cases for the purpose of 



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