180 PRACTICAL HISTOLOGY. 



go. If there is still no result the canula may be 

 pushed a little further in the sheath, and perhaps 

 moved a little to one side or the other in the hope of 

 thus rupturing a lymphatic and gaining an entrance 

 into the plexus. Should these and other devices 

 which experience may suggest still fail, the clip must 

 be replaced and another insertion tried elsewhere. 

 It very frequently happens that the injection which 

 escapes from the end of the canula, instead of pass- 

 ing into the lymphatics, forms merely a bulla of ex- 

 travasated fluid in the interstices of the tissue. This 

 can sometimes, by passing the handle of a scalpel 

 over it with moderately firm pressure, be induced 

 to find its way into the absorbent vessels, but if not 

 the canula must be withdrawn and re-inserted as 

 before. 



For the lymphatics in the fibrous substance of the 

 aponeurosis the canula must be inserted obliquely 

 into the tendinous tissue, and the injection forced 

 in with the same precautions. The pressure may, if 

 necessary, be raised somewhat higher, for, owing to 

 the firmness of the tissue, there is less liability to 

 the occurrence of extravasations. 



For displaying these injected preparations they 

 may, if injected with Berlin blue, be first placed in 

 spirit to remove all water and precipitate the color- 

 ing matter in the vessels (the process being completed 

 by putting the injected part into absolute alcohol), 

 after which the preparation may be placed in turpen- 

 tine and mounted in dammar varnish. Another 

 method, and one which succeeds very well, especially 

 with the alkanet injection, is to stretch the injected 

 aponeurosis over a ring of cork and allow it slowly 

 to dry by exposure to the air. When completely 

 dry the injected part may be at once mounted in 

 dammar or in glycerine. By this mode of proceed- 

 ing the injection is, as pointed out by Bowditch, 

 rendered more complete, for the fluid which may 

 have been extravasated in the interstices of the tissue 

 is apt to become drawn into the lymphatic vessels 



