124 PRACTICAL HISTOLOGY. [ill. 



remove as much aniline oil as possible. Wash the preparation several times 

 with xylol to remove the last traces of the aniline oil and mount in xylol- 

 balsam. 

 The stages are as follows : 



1. Harden in alcohol. 



2. Stain 5-15 minutes in concentrated aniline water solution of gentian 



violet. 



3. Dry with blotting-paper. 



4. Apply iodine solution (2-3 mins.). 



5. Dry with blotting-paper. 



6. Decolorise and wash in aniline-xylol. 



7. Remove the latter and mount in xylol-balsarn. 



(a.) Observe the threads of fibrin very fine and numerous stained a beau- 

 tiful violet. 



22. Solvent Action of Serum. Place some blood of a rabbit or guinea-pig 

 in a drop of blood serum of a dog. The red corpuscles are completely dis- 

 solved in a few minutes. The blood-corpuscles of a pigeon or frog are similarly 

 but more slowly dissolved, except the nuclei. This property of dog's serum is 

 set aside by previously heating the serum to 5o-6o C. for about half-an-hour. 



LESSON IV. 

 EPITHELIUM (STRATIFIED) AND ENDOTHELIUM. 



Epithelium presents the following general characters : 



1. It is always disposed on surfaces. 



2. The cells are united by cement. 



3. There are no blood-vessels within the cells. 

 Varieties of Epithelium. 



1. Squamous. 



2. Columnar. 



3. Secretory. 



4. Transitional. 



5. Ciliated. 



Squamous Epithelium may occur either in a single layer, or in 

 several layers ; in the former case it is sometimes called endothelium. 

 in the latter it is said to be stratified. 



(A.) In a single layer it lines serous and synovial membranes, 

 heart, blood- and lymph-vessels, air-cells of lung, pigmentary layer 

 of retina, posterior surface of cornea, anterior surface of iri ;, 

 membranes of brain and spinal cord, surfaces of tendons and tendon 

 sheaths, &c. 



