XVIII.] THE LYMPHATIC SYSTEM. 199 



4. Prepare sections of a spleen injected with Berlin 

 blue from the splenic vein under a low pressure. 

 Observe 



a. The veins in the trabeculae filled with injec- 

 tion material. 



h. The veins of the pulp more or less distinctly 

 branching out from the trabeculae. 



c. The irregular masses of injected pulp at the 

 ends of the veins. 



If the pressure used in injecting has been high 

 the splenic pulp will be permeated with blue as 

 with an arterial injection under high pressure. 



5. Cut across a fresh spleen, preferably one from 

 which the blood has been removed by injecting 

 normal salt solution through the splenic artery, 

 and examine the cut surface with the naked eye. 

 Note the white Malpighian corpuscles. With 

 curved scissors cut out one including some sur- 

 rounding tissue, and tease it out well in normal 

 salt solution. Observe the large number of 

 leucocytes of very variable size floating about, 

 some not distinguishable from white blood- 

 corpuscles, others twice, others three times as 

 large ; in some of the cells scattered about will 

 be seen brownish-red fragments, stages of the 

 breaking down of red blood-corpuscles. Try to 

 make out the constituents of the reticulum 

 (§ 2, h). 



