THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN 



VoL.XIIL] JULY, 1922. • [Xo. 14. 



The Size of the Thymus Gland in Relation to the Size 



and Development of the Foetal Pig as Studied in a 



Varied Range of Stages. 



BY DONALD X. MEDEARIS AND ALEXANDER MARBLE. 

 From the Laborator>- of Comparative Anatomy, University of Kansas. 



INTRODUCTION. 



THE thymus gland has long been a favorite subject for study 

 and for speculation as to its fimction and possible effect upon 

 gro\\i:h. ^Much work has been done in extirpation of the gland in 

 postnatal animals in order to note the effect upon metabolism. Dif- 

 ferent results have been obtained as different species of animak 

 were examined, depending largely upon the time of involution of 

 the gland in that particular animal. H. Matti (1) found that ex- 

 tirpation of the thymus in pups (eighteen days to eight weeks 

 in age) caused slowness of movement, muscular weakness, softness 

 of bones, bone changes resembling those in rickets, and subsecjuent 

 death. Almost similar results were reported by Basch (2i. Such 

 findings would seem to indicate a direct effect upon bone formation, 

 and accordingly upon the size of the animal. That the size of 

 thymus is correlated with size of animal ii. e., in individuals be- 

 low age of involution stage) is evidently accepted as probable 

 by Badertscher (3K who states in a description of a sketch that 

 "[above is an] outline drawing of the exposed left thymus of a 

 'runty' pig, one day old and only 240 mm. in length; the thymus 

 in this specimen was a few millimeters shorter than that in the full- 

 term embryo; this is perhaps due to the fact that the specimen was 

 a 'runt.' " On the contrary-, Hatai (4), in a study of postnatal rat 

 thymi, states that "the weight of the thymus is correlated with the 

 age of the rat rather than the body weight," thus showing a counter 

 finding. 



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