6 7 - 



LESSON XVII. 



SIMPLE ADENOID TISSUE. THYMUS, 

 LYMPH GLAND, AND SPLEEN. 



(a) Simple or Diffuse Adenoid Tissue. 



A portion of the vermiform appendix of a rabbit was hardened 

 in absolute alcohol, stained in borax carmine, embedded in paraffin, 

 and cross-sectioned. Fix to the slide, and mount in balsam. 



Examine under high power. The mucosa and sub- 

 mucosa form a continuous zone of adenoid tissue. The 

 mass of round cells are so closely packed that they cover 

 up the adenoid reticulum in which they are found. Sketch 

 as seen under high power. 



(b) Tonsil. 



The tonsil of a dog was hardened in mercuric chloride, stained 

 in Delafield's hsematoxyliu, embedded in paraffin, and sectioned. 

 Fix and mount in balsam. 



Study first under low power. Under the stratified 

 pavement epithelium are found a number of round or oval 

 nodules of adenoid tissue embedded in diffuse adenoid tis- 

 sue. They are more or less completely separated from the 

 surrounding tissue by a fibrous tissue envelope. Under 

 high power it will be noticed that in many places cells from 

 the adenoid tissue have wandered into the epithelium, often 

 to such an extent that it is difficult to recognize the epithe- 

 lial cells. One or more small mucous glands are often seen 

 in sections of the tonsil. Sketch under low power. 



(c) Thymus Gland. 



The thyrnus gland of a new-born mammal was hardened in 

 mercuric chloride, stained in Delafield's hiematoxylin, embedded in 

 paraffin, and sectioned. Fix and mount in balsam. 



Study under low power. The gland is divided into 



