148 PRACTICAL HISTOLOGY [XVIII 



the outline of an area is often not equally distinct all 

 round; and (h. p.) the leucocytes in places between 

 the epithelium cells. 



NOTES. 



Preservation of lymphatic glands. A cat or dog is killed (best by 

 bleeding after chloroform has been given) aud warm salt solution is 

 injected into a carotid for a quarter to half-an-hour, the lymphatic 

 glands of the neck are then cut out and placed in ammonium bichro- 

 mate 5 p.c. for about 3 weeks, sections are cut with a freezing microtome 

 and shaken. In sections so prepared the lymph channels are almost 

 completely free from leucocytes, and by careful and more prolonged 

 shaking they may be removed very largely from the follicles and 

 medullary cords. The leucocytes are more easily removed if sections 

 are cut a few days after the tissue has been placed in ammonium 

 bichromate, but further hardening is desirable. 



Injection of lymphatics of lymphatic gland. Take up in a Pravatz 

 syringe about 5 c.c. of a 2 p.c. solution of Prussian blue (Berlin blue), 

 pass the point under the capsule of lymphatic gland of a freshly killed 

 animal and slowly press the fluid in, squeezing the gland slightly with 

 the fingers. Place the gland in 95 p.c. alcohol for a week or more. 

 Place a piece for a day in absolute alcohol faintly tinged with eosin. 

 Imbed in paraffin. 



To show the outlines of the lymphatic epithelioid cells the gland 

 is injected first with '75 sodium sulphate solution and then with 

 2 p.c. nitrate of silver ; the gland is cut frozen and the sections 

 gently shaken in water and exposed to light. 



Injection of lymphatics. The lymphatics of the sub-cutaneous 

 tissue, of membranes, of the sheath of tendons, may be injected in 

 the same way as the lymphatic glands. If a bulla forms and does not 

 disappear with gentle pressure shift the point of the injection needle, 

 or make another puncture. It requires considerable care and practice 

 to make successful injections. 



Natural injection of lymphatics of diaphragm. Ten to fifteen c.c. 

 of a saturated solution of Prussian blue is injected into the abdominal 



