4 8 



culae ? Understand the relation of the afferent and efferent lymph 

 vessels to the gland and the course of the lymph through it. 



94. Thymus. Transection. ; paraffin ; sec- 

 tions IJL. Stain with hematoxylin 15 minutes, picrofuchsin 30 

 seconds. 



Compare this preparation carefully with 93, identifying as be- 

 fore, capsule, trabeculae, cortex and medulla, lymph follicles (nod- 

 ules), and in addition, the lobular structure. Can you find corpus- 

 cles of Hassall ; what is their significance? Study the structural 

 appearance of the organ so that you may distinguish it from 93 and 

 95. Study the microscopic appearance of the thymus. 



95. Spleen. Dog. Transection. vom Rath's ; collodion ; 

 sections yw. Stain with hematoxylin 15 minutes, picrofuchsin 

 30 seconds. 



Examine the gross preparations of the spleen, observing care- 

 fully the structural appearance of natural and cut surfaces. Study 

 the microscopic preparation, recognizing (a) the capsule and the 

 trabeculae ; is plain muscle present in these ? () the splenic pulp 

 containing the Malpighian corpuscles (lymphatic follicles or nod- 

 ules), and blood vessels. Examine the Malpighian corpuscles, not- 

 ing their structure and the eccentric artery ; compare them with the 

 lymphatic nodules in 93 and 94. ' For the supporting framework of 

 the spleen, the capsule and trabeculae, examine the gross, mace- 

 rated preparation. Study carefully the general structural appear- 

 ance of the section of spleen, so that you may distinguish it from 

 lymph gland or thymus. Again consult the gross section of spleen, 

 identifying capsule and trabeculae, Malpighian corpuscles and 

 splenic pulp. Understand the relation of the blood vessels to the 

 Malpighian corpuscles and to the pulp. 



