RELATIONSHIP OF ENDOCRINE ORGANS TO GROWTH 499 



tial excision leads to underdevelopment and particularly to retarded 

 development of the bones (Fig. 38). In amphibians complete removal 

 of both parts of the hypophysis is possible at a very early stage of 

 development and Smith has shown that in hypophysectomized tad- 

 poles development and Metamorphosis are very strikingly retarded in 

 comparison with the normals, while the skin remains unpigmented and 

 the tadpoles have the appearance of albinos. The albinism, but not 

 the defective development, may be cured or prevented by the adminis- 

 tration of posterior-lobe extract. 



Feeding experiments in which pituitary tissue is administered to 

 normal animals have yielded uniform, but by no means striking 

 results. The Posterior-lobe tissue leads to loss of weight and intestinal 

 disturbances which are not attributable to or indicative of any effect 

 upon growth. The administration of Anterior-lobe tissue to rats has 

 been observed by Aldrich and by Schafer to cause retardation of early 

 growth, followed, in Schafer 's experiments, by a secondary accelera- 

 tion. Wulzen and Maxwell, working with fowls, likewise obtained retar- 



r CRAMS, 



Normal 



IVeeKs 



4 10 ZO 30 40 60 



FIG. 39. Comparison of the growth-curves of normal and of pituitary-fed female white 



mice. 



dation followed by acceleration and the same effect has been observed 

 in mice (Fig. 39). The uniform testimony afforded by all of these 

 experiments is therefore that the administration of anterior-lobe tissue 

 causes initial retardation and a secondary acceleration of growth, but 

 both of these effects are slight. 



The inconspicuous character of these results is probably to be 

 attributed to the fact that of all the tissues of the body, the Anterior 

 Lobe of the pituitary gland is the one most richly supplied with blood. 

 The circulation is in fact extraordinarily efficient and we may infer 

 that the active product or products of the gland leave it very rapidly 

 and do not accumulate therein. Hence the dosage of the active mate- 

 rial which happens to be present in the gland at the moment of death of 

 an animal may represent but a fraction of the quantity which is manu- 

 factured and discharged in the course* of a day. When we administer 

 pituitary tissue we are seeking to imitate or accentuate by a single 

 daily administration of merely residual material, the action of a gland 

 which is engaged every moment of the day in manufacturing and 

 discharging the substance which influences the growth of tissues; 

 we cannot, therefore, look for large results. As we shall see, much 

 more decisive effects can be elicited by the administration of a con- 



