ATROPHY OF THE ORGANS OF THE LARVAL FROG. l6l 



Experiment. Tap water was boiled and cooled in hermetically 

 sealed jars. Finger-bowls were filled with the water and larvse 

 introduced. There was a high mortality amongst the larvae, 

 but a few were kept for two weeks, during which time no meta- 

 morphosis occurred. 



Experiment. The dorsal nerve cord together with the aorta 

 was ligated with silk thread, at the base of the tail. Again, the 

 mortality was high, the open cut being attacked by Saprolegnia 

 and water moulds, wild yeasts, etc. No acceleration in meta- 

 morphosis was observed. 



Lack of oxygen, or a marked reduction in its amount does not 

 induce autolysis in the larvae. It must be admitted, however, 

 that the negative results of the last experiment do not bear out 

 the theory that interference in the blood supply induces atrophy. 

 Lateral circulation, however, may have been a factor. 



Wintrebert (23), seeking the cause of atrophy in the larval 

 frog, suggested that an internal secretion induces metamorphosis. 

 The following experiment was directed towards the obtaining of 

 evidence upon this pojnt: 



Experiment. Five normal larvae were isolated in large petri 

 dishes. Serum was injected into the dorsal lymph sacs of these 

 larvae, the serum having been obtained either from the blood of 

 involuting larvae or from the expressed juices of the tail. No 

 attempt to keep the preparation sterile was made owing to the 

 obviously impossible nature of the task. The results were 

 negative as far as inducing metamorphosis. 



Attention has been directed to the glands of internal secretion. 

 Thus Babak (24) has studied the effects of injections of hypo- 

 physis and of other portions of the brain. Positive results were 

 obtained which this writer interpreted as due to direct effects 

 upon the nervous system rather than upon the tissues. Babak 

 considers that there is a hormone-action involved in the sense of 

 Bayliss and Starling. The thyroid has received a relative large 

 amount of attention. Gudernatsch originally observed a pre- 

 cocious metamorphosis in the case of larvae fed upon thyroid 

 preparations and since his work, others have studied the problem 

 from the biochemical aspect. David Marine (25), Lenhart, the 

 writer (26) and recently, from a more general physiological 



