EFFECTS OF EXTIRPATION OF THYROID GLAND 569 



MATERIAL AND TECHNIQUE 



The material from which these observations were made was 

 collected near Lawrence, Kansas, during the early spring of 

 1916 and the thyroid gland was removed by Professor Allen 

 when the Eana pipiens were about 6 to 6.5 mm. in length. 

 About one half of the number collected were operated upon and 

 the remainder were kept as control specimens. 



The metamorphosis of the control specimens began about 

 the middle of July and continued until August 13, while the 

 operated tadpoles failed to metamorphose and continued to 

 live on in their larval state maintaining largely their larval 

 characteristics. These specimens both thyroidless and normal 

 controls have been killed at various times ranging from July 

 25, 1916 to March 28, 1917, so as to trace the development of 

 the skeletal system as clearly as possible. 



As to the method of study I may justly divide it into three 

 parts. First, a study of whole mounts, cleared by the Schultze 

 caustic potash glycerine method; second, a microscopical study 

 of sagittal and transverse sections of the vertebral column; 

 and third a study of the cartilage and bones of the hind legs 

 stained 'in toto' by means of the Lundvall method. 



In the first method the whole mounts are prepared, after 

 measurements have been taken and fixation has been accom- 

 plished, by first placing the entire specimen in a two per cent 

 solution of potassium hydroxide. It is left in this solution for 

 about eight to ten days, after which it is placed in a twenty 

 per cent glycerine solution for clearing where it is kept for about 

 two days; it is then placed in a stronger solution for an equal 

 length of time and so on until a full strength glycerine solu- 

 tion is reached where the whole mount may be studied and 

 kept indefinitely. In specimens which have thus been treated 

 we find that the cartilage appears transparent while the bone 

 appears more or less opaque. 



Coming now to the second method, viz., that of a microscop- 

 ical study of sagittal and transverse sections, which if any 

 distinctions are to be made between the methods of study, 



