Blood Vessels. 79 



be enough. They must be allowed to stain very gra- 

 dually, as the logwood takes some time to penetrate the 

 capsules. The solution of logwood must be changed 

 several times as it is apt to become granular. It will 

 take about 48 hours or longer, to stain the corpuscles 

 thoroughly. When they have taken in the colour suf- 

 ficiently, wash them well in plain water and mount in 

 glycerine. 



Vertical sections should also be made of the pad of 

 a cat's foot, hardened in chromic acid mixture and 

 stained in logwood. 



BLOOD VESSELS. 

 CAPILLAKIES. 



Take the tail of a half-grown Tadpole or common 

 frog, and place it in a 5 per cent, solution of chromate 

 of ammonium for 24 hours to remove the epithelium, 

 then wash well until no colour comes away in the 

 water, and double stain with carmine and indigo- car- 

 mine (page 37). Mount in Canada balsam. 



By this process the capillaries will be deeply stained 

 with carmine, and can be seen in their natural con- 

 dition. 



Examine the capillaries, in a gold preparation, of 

 a Tadpole's tail stained with logwood. 



Either of these preparations will show them in pro- 

 cess of development from branched connective corpus- 

 cles. Examine them carefully for the nuclei of the 

 walls, and observe in many the contained blood cor- 

 puscles. 



