GEOWTH OF AMPHIBIA AFTER THYROIDECTOMY 19 



maximum length their entire metabohc process is very unstable, 

 and at this time some slight influence, say of the thyroid and 

 perhaps also of the hypophysis, is able to furnish the stimulus 

 necessary to upset this process and so to initiate the series of 

 vital phenomena which we call metamorphosis. 



From the point of view of age, it may be considered that the 

 growth of the body of the thyroidless larvae as a whole, or of 

 most of their organs is precocious, since in a given time they 

 grow more rapidly than the control larvae. The skeleton as a 

 whole and the brain grow more slowly than those of the controls. 

 If thyroidless larvae are compared with control larvae of the 

 same size regardless of age, then the only very precocious growth 

 noticeable is that of the hypophysis. 



Organs and method of comparison 



The following figures representing the condition of the organs 

 of the animals studied are all camera-lucida drawings of the 

 organs removed in autopsies or studied in microscopical sections. 

 The number of complete autopsies performed was sixty-nine. 

 In addition there were done about forty partial autopsies. In 

 addition to these, many larvae and frogs were sectioned serially. 

 For comparison of the organs, outline drawings were made and 

 the drawings afterward were compared directly. Measurements 

 were made of the various diameters of those organs of regular 

 contour, but most of the organs are so irregular in outline that 

 such measurements are of little or no value, and the accompany- 

 ing pictures give a much better idea of the conditions obtaining 

 in most of the organs than would any tables, no matter how 

 carefully prepared. It should be noted that the accompanying 

 figures are drawn from specimens which were carefully chosen 

 as representing the condition as near the average as possible. 



The organs are in most cases too small for direct volumetric 

 determinations. Allen ('18) and Rogers ('18) have used the 

 product of the three principal diameters of an organ to represent 

 its volume, but this is not even approximately correct, because 

 of the great variation in the shape of most organs of larvae and 



