136 NORMAL HISTOLOGY. 



A node being exposed in a recently killed animal one of 

 the cervical nodes of the dog answers well a hypodermic 

 syringe is warmed and filled with the warmed blue 

 gelatin mixture ; the canula is now thrust through the 

 capsule at any point, and the fluid injected. The node 

 will become mottled with blue, and the mass will often be 

 seen to flow into adjacent nodes. If it be not desired to 

 inject more than one, a ligature should be passed around 

 the vessels leading to the others. When a sufficient 

 quantity of the fluid has been injected to render the node 

 firm and the capsule tense, the canula is withdrawn, and 

 the node cooled by ice or cold water. When the gelatin 

 has solidified, the node is cut out, divided longitudinally, 

 and put into strong alcohol. When it has become suffi- 

 ciently hard, sections are made through the entire node, 

 stained with picro-carmine or alum-carmine, and mounted 

 in balsam. 



Blood-vessels. To obtain an injection of the blood- 

 vessels of the lymph-nodes, either a whole animal, such 

 as the rabbit or dog, may be injected through the aorta, 

 with the blue gelatin mixture ; or a single node, such as 

 the cervical or mesenteric, may be injected through its 

 main artery. The nodes should be hardened in alcohol, 

 and the sections stained deeply with eosin and mounted 

 in balsam. 



THE SPLEEN. 



The spleen, although differing in many important 

 and probably most essential particulars from the 

 lymphatic glands, yet presents many striking analo- 

 gies with them. Like them, it presents, on cross- 



