466 J. A. BADEBTSCHER 



passed into it from blood vessels but regards the thymus as a 

 source of some of the "colored blood corpuscles." 



Prymac ('02) holds that during involution of the teleostean 

 thymus numerous red blood cells are formed from the small 

 round cells. Erthrocytes also escape into the parenchyma 

 from the blood vessels. All undergo degeneration. The prod- 

 ucts of degeneration of the greater number of red cells are gran- 

 ules which are taken up by indifferent thymus elements, while 

 that of the smaller portion is in the form of pigment which 

 accumulates in masses in the parenchyma. 



Schaffer ('93) in the thymus of the rabbit and cat found red 

 blood-cells in various stages of development, and transition 

 forms between the leucocytes and nucleated red blood-cells. 

 He believes that the thymus has a hematopoietic function. 



Bell ('06) in the thymus of a 240 mm. pig found numerous 

 erythrocytes, lying singly and in groups, in the cortex while 

 free erythrocytes were rarely to be found in the medulla. He 

 does not consider their origin. 



Maximow ('09) was not able to recognize definite erythro- 

 blasts or transition forms in the parenchyma of the thymus but 

 thinks that lymphocytes have been confused with them. In 

 the interlobular septa, however, he found collections of erythro- 

 blasts and normoblasts, or briefly, all transition forms from large 

 lymphocytes to erythrocytes. He does not believe that red 

 blood-cells are formed in the thymus. 



Other investigators have observed free erythrocytes in the 

 thymus in various stages of its development. Some make no 

 mention of their origin while others suggest a possible origin 

 but do not trace out their cytomorphosis. 



Granular cells have been observed in the thymus by many 

 investigators but the views regarding their origin and nature, 

 which will be only briefly summarized, are conflicting. During 

 the latter part of fetal life and the remaining period of growth 

 and involution, Watney ('82) found in the medulla of the thymus 

 of birds, reptiles, and mammals many granular cells. He divided 

 them into 'four classes which were connected with each other by 

 intermediate forms. He found them especially numerous along 



