154 Modern Microscopy 



dry weather, as any moisture in the air retards the drying of 

 the corpuscles, and then they are hable to change their form. 



Epithelium. — Kill a frog, cut off its head, and remove 

 the lower jaw. Open the abdomen and take out the 

 stomach, and slit it open. Place the head, lower jaw 

 and stomach in a 2 per cent, solution of bichromate of 

 potash for forty-eight hours. Then wash gently in water 

 until no colour comes away from the specimens. Now 

 place all three portions in picrocarmine for twenty-four 

 hours. Eemove the tissues from the carmine, and allow the 

 stain to drain away from them. Take the lower jaw and 

 scrape the tongue for squamous epithelium, and place the 

 deposit obtained in a few drops of glycerine on a slide. 

 Take the stomach, remove some columnar epithelium from 

 its internal surface, and place it in some glycerine on 

 another slide. Then take the head for ciliated epithelium, 

 which will be found at the hinder part of the roof of the 

 mouth ; put some scrapings from this in glycerine on a slide 

 as before. Clean a slide and place a drop or two of Farrant's 

 medium on its centre ; take up a little of the epithelium on 

 the point of a needle, and put it into the medium. Now 

 apply a cover-glass, and with the needle-point press it down 

 until the epithelial cells are separated and spread evenly 

 between the cover and the slide. Set the slide aside for a 

 day or two, so that the medium may set. Then wash away 

 the excess of medium with some water and a camel's hair 

 brush, dry the slide with a soft rag, put it in a turn-table, 

 and run on a ring of ceinent. 



Portions of the tongue, trachea and intestine of a rabbit 

 or cat may be treated in the same way. 



Endothelium. — Take a piece of the omentum of any 

 small animal, and rinse gently in distilled water to remove 

 soluble matter. Place it in a :i per cent, solution of silver 

 nitrate for ten minutes, or until it becomes a milky white. 

 Wash well in ordinary water, and expose in a saucer of 

 water to diffused sunlight, until it assumes a brownish 

 colour. Cut out a small piece and mount it in Farrant's 



