EXTIRPATION OF ANTERIOR LOBE OF HYPOPHYSIS. 121 



We shall now take up a detailed account of the different ex- 

 periments that bear upon the subject of this paper. 



No. 13. April 9 and IO, 1916. Length at time of operation 

 5.5 mm. These tadpoles were in too advanced a stage of de- 

 velopment to give satisfactory results. It was impossible to 

 clearly see the hypophysis ingrowth because it had become so 

 much broadened and flattened. The ventral surface of the fore- 

 brain was scraped and frequently injured in the process. Under 

 this heading are included three series of experiments. 



(a) April 9. 14 operated, rather crudely. 10 remained alive 

 at the end of 9 days. These were discarded because of later 

 improvements in technique. 



(b) April 9. 12 operated. The work was much more care- 

 fully performed than in (a). The under side of the fore brain was 

 carefully scraped and all specimens that showed injury to the 

 brain were discarded. 6 remained alive at the end of II days 

 when they were preserved for sectioning. 



(c) April 10. 20 operated. In this case the floor of the dien- 

 cephalon behind the optic stalks was removed in order to insure 

 the complete removal of the hypophysis which in itself is quite 

 hard to recognize at this late stage. Only 3 remained alive at the 

 end of 6 days and they were distorted. 



These experiments were made at entirely too late a stage of 

 development to be successful. They are merely given to show 

 the stages through which the work progressed. 



No. 14. (a) April 10. 12 operated. 3 alive at the end of 6 

 days. Length at time of operation 4 mm. This was the first 

 really successful experiment. This unfavorable result was purely 

 due to neglect owing to the press of work in later experiments. 

 The remaining specimens were killed. 



(&) April ii. 65 operated. Tadpoles kept in a finger bowl 

 for 2 days when it was found that 20 showed abnormalities due 

 to lack of oxygen. These were isolated, some dying within a 

 few days while others partly recovered. These were later dis- 

 carded. Of the remaining 36 healthy tadpoles 31 were alive at 

 the end of 26 days. During this time they were kept in soft 

 cistern water. They were fed algae which helped to oxygenate 

 the water in the aquaria. The close quarters of the aquarium 



