658 MR. E. A, SPAUL ON THE 



tissue and tlie failure of thyroidless tadpoles to change until 

 given either thyroid diet or iodine, followed by the conversion of 

 axolotls to salamanders by thyroid diet, showed conclusively the 

 importance of the thyroid and thyroid iodine. Although pitui- 

 tary diet does not induce metamorphosis in either tadpoles or 

 axolotls, pituitaryless tadpoles fail to transform, whilst axolotls 

 injected with extract from the anterior lobe of the pituitary 

 gland assume adult characters as rapidly as individuals treated 

 with thyroid, which is evidence in favour of the significance of 

 the anterior lobe of the pituitary in metamorphic changes. 



The results of experiments briefly outlined here show that the 

 anterior lobe contains an active principle functioning in a definite 

 maimer in metamorphosis. Previously only young axolotls had 

 been used, but larger specimens, in some cases beyond that size 

 at which they change in normal environment, were taken, and by 

 tri-weekly injections caused to transform to adults. The rate of 

 metamorphosis depended on the size of the animal and the temi)eia- 

 ture. The first signs of change appeared much later in the older 

 specimens, but providing the dose was sufficient the process was 

 more rapid. Within two or three weeks of the first injection the 

 change begins and is usually complete by the 40th day in medium 

 size or the 48th day in the oldest types under suitable conditions 

 of tomperature. The limits of the latter are 22°-24'^ C, when the 

 animal remains quite normal thioughout the experiment. Low 

 temperature retarded the change, and if too high the animal 

 became sluggish, refusing food, with no noticeable increase in 

 the rate of change. 



The approximate limits of the minimal dose were found, but 

 it was not possible to give any relation between tlie minimal 

 dose within these limits and the weight, as the complexity of 

 the factor.-;, both internal and external, made the production of 

 identical conditions each time, and hence uniformity, impossible. 

 The limits were '5 grs. of fresh gland per -5 c.c. injection for 

 small individuals to 1"5 grs. for full-grown animals. 



Weights and measurements were taken on days alternating 

 with those upon which injections were made throughout the 

 period of the experiment, but no increase in growth was noted, 

 only a decrease. This does not deny the growth-promoting 

 properties of the anterior lobe, for the animals used were adult 

 and sexually n)ature, so that reduction previous to metamorphosis 

 was to be expected. 



Having ascertained these details, the change resulting from 

 the injection of the anterior lobe extract was applied aa a 

 biological test in the examination of the purity and strength 

 of commercially prepared extracts. Quantities up to 1/10 of a 

 clinical dose could be tested in this manner. Of twelve so tested 

 only one successfully brought about the change, although as 

 many as 20 injections were made. The dose was the same in 

 each case, the quantity stated by the manufacturer being taken 

 as a basis and equivalent to the minimal dose as found in previous 

 experiments, 



