Il8 W. W. SWINGLE. 



Pappenheimer extirpated the thymus of young albino rats 

 and found that removal had no effect upon body growth and 

 development. 



Adler extirpated the thymus of tadpoles and found that these 

 animals suffered no ill effects from the operation. Growth and 

 development was unaffected. 



(The work of Gudernatsch has been noted.) 



This rather extensive review of the literature was thought 

 justifiable in view of the discrepancy in the results obtained by 

 the various investigators. 



MATERIAL AND OBSERVATIONS. 



The following experiment began May 3, 1915, and was com- 

 pleted July 29, 1916. The work in 1915 dealt with the effect 

 of feeding thymus powder to tadpoles, the work for 1916 was 

 concerned with those experiments in which only the fresh gland 

 was employed as food. I shall discuss the work dealing with the 

 fresh gland first, and devote the latter part of this paper to 

 feeding experiments with thymus powder. 



FEEDING FRESH THYMUS GLAND. 



This work began April 12, 1916. April 2, the eggs of Rana 

 pipienswere gathered from a group of shallow pools near the Uni- 

 versity campus at Lawrence, Kansas, and allowed to develop in 

 the laboratory. One group of eggs was hastened considerably in 

 development by keeping them in a warm room. When the 

 young larvae had emerged from their gelatinous egg capsules 

 and developed to the free feeding stage, they were placed in 

 glass bowls ten inches in circumference by four inches deep. 

 The tadpoles were covered with ordinary tap water which was 

 changed daily. 



When the larvae had attained a length of nearly 13 mm., 

 one hundred and fifty were selected, and divided into two 

 groups of seventy-five each; one lot was destined for thymus 

 feeding, the other for control purposes. These two lots of 

 seventy-five animals were then subdivided into lots of ten and 

 placed in glass bowls, one lot to a bowl. Both control and 

 experimental larvae were reared under identical conditions as 

 regards temperature, light and water supply. 



