n8 



BENNET M. ALLEN. 



account of these experiments with a full account of my work upon 

 thyroid removal. Since six of the tadpoles in the latter experi- 

 ment are still alive and the work upon the preserved material 

 far from complete it seemed after all advisable to publish separate 

 papers upon the two lines of work. 



In the present serievS of experiments the removal of the hypo- 

 physis ingrowth was accomplished by making a frontal cut just 



FIG. i. 



beneath it and extending more than its entire length as shown 

 in Fig. i. It was then quite a simple matter to open up the 

 wound and remove the hypophysis ingrowth by means of a 

 spear-point needle. This was performed under a binocular 

 microscope. The stage chosen for operating is that of 3.5 to 4 

 mm., the operation being performed more readily at this time 

 than later because at this stage the ingrowth is compact and 

 thick, but later becomes thinned out and more closely applied 

 to the diencephalon, thus increasing the difficulty experienced in 



