182 THE ORGANS 



Stohr denies the mesodermic invasion of the thymus and consequently the 

 lymphatic character of the gland. He considers the specific cells of the thymus 

 as modified epithelial cells which have become "deceptively like lymphoid 

 cells." This explanation has not, however, been generally accepted. 



TECHNIC 



Fix the thymus of a new-born infant in formalin-Miiller's fluid (technic 6, p. 

 7), and harden in alcohol. Stain sections with hsematoxylin-eosin (technic i, 

 p. 20), or with haematoxylin-picro-acid-fuchsin (technic 3, p. 21), and mount 

 in balsam. 



The Tonsils 



The Palatine Tonsils or True Tonsils. — These are lymphatic 

 organs, essentially similar in structure to those already described. 



V 



V 



Fig. 107. — Vertical Section of Dog's Tonsil through Crypt. X15. (Szymonowicz.) 

 a. Lymph nodule; b, epithelium of crypt; c, blood-vessel; d, crypt; e, connective-tissue 

 capsule; /, mucous glands; g, epithelium of pharynx. 



The usual librotis capsule is present only over the attached sur- 

 face, where it is firmly adherent on the one side to the tonsillar 

 tissue and on the other to the surrounding structures from which it 



