590 JAMES B. ROGERS 



'00). 2 This theory however is not generally accepted. There 

 is much controversy as to the thymus being essential to life. 

 Some writers say it is not but that its removal has an effect 

 upon the sex glands. Gudernatsch ('14) 3 says that thymus 

 feeding increased the growth, but retarded differentiation in frog 

 tadpoles. 



The material was furnished by Prof. B. M. Allen and was 

 used by him in his experiments upon the removal of the thyroid. 



The controls consisted of a number of tadpoles raised under 

 the same conditions as the thyroidless and a number of normal 

 frogs in various stages before, during and after metamorphosis. 



In the stages up to and including the 24 mm. stage the speci- 

 mens were prepared for study by sectioning the head portion 

 which contains the pituitary and the thymus. The sections 

 were stained with Haidenhain's iron alum-haematoxylin and 

 eosine. 



The glands were measured by taking the two dimensions 

 from each section in the series and by counting the sections and 

 multiplying by the thickness to get the other dimension. The 

 average measurement of each dimension times the average of 

 the other dimensions furnishes a means of comparing the glands 

 for size. With an eye piece micrometer the longest diameter 

 of the gland in any given section was measured. Then the 

 micrometer was turned at right angles to the first dimension 

 and the reading recorded. 



In the later stages the desired measurements were obtained 

 in a different manner. The specimens were too large to be 

 readily sectioned through the head. Accordingly they were 

 pinned on paraffin under a binocular microscope and the thy- 

 mus was then exposed and dissected. Each gland was then 

 put in a shallow dish and drawn with a camera lucida. The 

 gland was first drawn showing the outline in a plane perpendic- 

 ular to the shorter diameter. Then it was set up edgewise in 

 a small groove cut in the paraffin so that the second drawing 

 showed the outline in the plane of the shorter diameter. After 



2 Beard, J. 1900. Anat. Anz., Bd. 18. 



3 Gudernatsch. 1914 Am. Jour. Anat., vol. 15. 



