494 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



of the uterus is a striking example of the intensity and specificity of 

 growth-stimulation which may be brought about by agencies of this 



type. 



It is possible that not all of the organs of internal secretion which 

 are capable of affecting and modifying the growth of animals do so by 

 virtue of growth-catalyzers which they elaborate. Thus hyperactivity 

 of the thyroid leads to generalized loss of body-weight owing to a 

 marked increase of metabolism and particularly of nitrogenous 

 metabolism, while hypo-activity leads to the peculiar maladjustments 

 of development which characterize the condition of myxedema. These 

 effects, however, are more probably due to a general action of the 

 thyroid principle in accelerating Exogenous Metabolism and reducing 

 the nutritional level in the tissue-fluids. They are effects which more 

 probably concern the concentration of the available substrates of growth 

 than the specific rapidity of their elaboration into protoplasm. The 

 disproportionate growth of connective tissues which characterizes 

 myxedema is more probably to be attributed to the absence of the 

 normal competition with the cellular elements for a limited supply 

 of substrates than to any specific stimulation ' of connective-tissue 

 synthesis. 



The function of the Thymus in growth is obscure and its true signifi- 

 cance may perhaps be rather that of a storehouse of substances, for 

 example Nucleic Acids, which will be required in subsequent develop- 

 ment than of a factory of growth-catalyzers. The relationship of the 

 anterior lobe of the Pituitary Body to the processes of growth is, how- 

 ever, clearer and more defined, and is of such a character as to en- 

 courage the supposition that in the hypophysis we have one instance 

 among others of an organ in which the function of growth-catalysis is 

 concentrated and specialized. 



The relationship of the pituitary gland to certain remarkable disturb- 

 ances of growth was first pointed out in 1888 by the French surgeon 

 Pierre Marie, who drew attention to two types of anomalous growth 

 which postmortem examination showed to be invariably associated 

 with abnormalities of the hypophysis. These rare pathological condi- 

 tions are Gigantism and Acromegaly. 



There are occasional individuals in whom, either before or during 

 adolescence, the growth of the skeleton undergoes an extraordinary 

 acceleration so that they attain such an abnormal stature as to attract 

 universal attention. Such are the individuals who are occasionally 

 exhibited as "giants" in shows and fairs (Fig. 35). A closer inspection 

 of these cases usually reveals other abnormalities which, in the adult 

 at all events may be of two opposite types. The skin may be thin, 

 transparent and hairless, the extremities small, muscular energy 

 deficient, the genitals imperfectly developed, and,, according to Gushing, 

 a decided intolerance for sugar is usually also present. On the other 

 hand cases may be encountered in which the reverse of these charac- 

 teristics may be noted, the skin is thick, coarse and hairy, the extremi* 



