IODINE AND AMPHIBIAN METAMORPHOSIS. 23! 



globulin fraction of the serum contained most of the iodine. It 

 was decided to try injecting iodoserumglobulin into thyroidless 

 axolotls, controlling the experiment by injections of equal 

 amounts of non-iodized globulin. The blood of beef was used. 



Three axolotls were each injected twice, at eight-day intervals 

 with no milligrams of iodoserumglobulin. Metamorphosis 

 resulted within twenty days following the first injection. One of 

 the axolotls had previously served as a control in the iodotyrosine 

 experiment and had been injected with pure tyrosine. The 

 results were negative and as the larva showed no indications of 

 metamorphosis several weeks later it was utilized in the iodo- 

 serumglobulin experiment. Two control thyroidless animals (pre- 

 viously used as controls in the iodotyrosine work) injected with 

 large amounts of non-iodized serumglobulin failed to transform. 



Dissection of the metamorphosed iodoserumglobulin-injected 

 animals showed two of them to have no vestige of thyroid tissue, 

 but the remaining one had a portion of the gland present on the 

 left side, an amount about equal to a third of the entire thyroid. 

 One of the controls was then injected with iodoserumglobulin 

 and metamorphosed twenty-one days after the first injection; 

 dissection of this animal also showed a small nodule of thyroid 

 tissue present. Thus four axolotls were metamorphosed by 

 injections of iodized serumglobulin; two of the animals were 

 completely thyroidectomized, and tw r o only partially. No very 

 marked difference in the time or rate of metamorphosis was noted 

 between the partially and completely thyroidectomized animals. 

 The axolotls possessing remnants of glands were the first to show 

 signs of transformation following injection, but the time differ- 

 ence was not over three days in any case. The fact that both 

 types of animals metamorphosed within a few days of each other 

 may have been due to the large amount of iodoserumglobulin 

 injected. It is probable that partially thyroidectomized animals 

 will be found to respond by metamorphosis to considerably 

 smaller doses than thyroidless animals. Axolotls were not 

 available to test this point. 



Considerable difficulty was experienced injecting the globulin 

 intraperitoneally. The solution of the problem while crude was 

 effective. A small incision was made through the ventral body 

 wall sufficiently large to admit the end of a graduated pipette 



