202 PRACTICAL HISTOLOGY. 



membrane outwards, instead of vice versd. But, 

 owing to the great difference in hardness between 

 the cartilaginous rings and the rest of the tissue, it 

 is difficult to get a complete section equally thin 

 throughout. 



Preparations 9-10. Bloodvessels and lymph- 

 atics of trachea. In addition to these sections flat 

 preparations showing the bloodvessels, and others 

 showing the lymphatics of the mucous membrane, 

 may be made. The former are got from any animal 

 that has been injected entire, the mucous membrane 

 being dissected off and mounted in dammar. The 

 lymphatics are readily filled by the puncture method 

 by sticking the point of the injecting canula into 

 the mucous membrane, and forcing a little Berlin 

 blue or alkanet-turpentine in. It will hardly ever fail 

 in finding its way into the numerous lymphatics of 

 the mucous membrane. The injected portion is dis- 

 sected off and mounted in dammar varnish or in 

 glycerine. 



Teased-out bichromate of potash preparations to 

 show the separated epithelial cells have already 

 been made (p. 67). 



Preparations 11-13. Ductless glands of the 

 larynx and trachea. The thyroid and thy m us 

 are studied chiefly by means of sections, for facili- 

 tating the preparation of which the glands are 

 hardened in alcohol. They should not be put 

 entire into this, but either cut into pieces or deep 

 cuts should be made into their substance, so that 

 the preservative fluid may penetrate rapidly. It is 

 well to place them at first in weak spirit (half water) 

 for twenty-four hours, and then to transfer them to 

 the strongest possible, in which they are allowed to 

 remain for a few days until hard enough to cut thin 

 sections from. Like most organs which have been 

 hardened in alcohol alone, they stain very readily. 

 The so-called "colloid" which is met with in the 

 vesicles of the thyroid is colored by the logwood. 

 Both glands may be advantageously obtained from 



