710 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 2 8 



the study of human cases, could be obtained from animal experi- 

 mentation. The other two methods of approach, use of extracts and 

 removal of the gland, failed to produce decisive results. Recently, 

 however, Evans and Smith, of the University of California, have 

 been able to show in a truly spectacular fashion the profound effect 

 which the anterior lobe has upon growth. They have been able to 

 prepare an extract of the anterior lobe which has this effect. The 

 experiments were carried out in this way : Pituitary glands (anterior 

 lobe) of the ox were minced and extracted with salty water. The 

 extract obtained in this simple way was then injected into young 

 white rats over a period of several weeks. Other rats of the same 

 litter were kept under precisely the same conditions and received the 

 same food, but were not injected with extract. These untreated rats 

 served as standards or controls, as they are technically called, to 

 which the injected rats could be compared. 



The period of growth of the normal laboratory rat is now well 

 known. It is from 150 to 180 days. At the end of this time it has 

 reached the adult form and size and ceases to grow further. The 

 control rats followed this normal course. The treated rats, that 

 is, those injected with the extract, did not cease to grow when the 

 end of this j^eriod was reached, but continued to grow for several 

 weeks afterwards. They finally developed into huge, giant rats. 

 Though they were not, perhaps, as large as the rats that Gulliver 

 adventured with in Brobdingnag, they were at least 60 per cent, and 

 in some cases 100 per cent, larger than their brothers and sisters of 

 the same litter which had received no extract. 



The other side of the picture was also outlined by experiment; 

 that is to say, depression of the pituitary function produced the 

 reverse effects, retarded growth. On account of the small size of the 

 pituitary in the rat it is impossible to destroy one part of the gland 

 without injuring or destroying more or less of the other part as 

 well. There is also the danger of damaging too severely the anterior 

 lobe, which is essential to life. It was therefore impossible to pro- 

 duce pure effects of one or the other lobe. The effects were what 

 might have been expected from partial destruction and consequent 

 deficiency of both lobes. The animals became very fat and failed 

 to grow to normal size. They corresponded very closely to the type 

 of dwarfs already described for human subjects as a result of defi- 

 ciency of both lobes. These animals, however, usually showed the 

 obesity more than the dwarfing; they were so rotund that they 

 resembled nothing so much as little balls of cotton wool. 



Before leaving the subject of the pituitary I must speak of another 

 strange effect which its secretion has upon certain members of the 

 amphibian and reptile families. Many of you no doubt have been 

 fascinated by the way in which some of these creatures, such as the 



