178 PRACTICAL HISTOLOGY [XXFI 



4. Transverse section through Lieberklihn's glands 

 of small intestine. 



5. Section showing passage of glands of rectum 

 to stratified epithelium at anus; note the continuity 

 of the submucous with the subcutaneous layers. 



NOTES. 



Preserving and staining. A short length of the intestine is washed 

 out with salt solution, then distended moderately with chromic acid 

 2 p.c., the piece still distended placed in chromic acid -2 p.c. for 

 a day. The ligatured ends are then cut off, and it is left in fresh 

 fluid for a week, washed in running water, passed through alcohols 

 up to 70 or 75 p.c. and so kept, best in the dark. Flemming's fluid 

 gives perhaps better results than chromic acid, in this the piece of 

 tissue is only left for a day ; sections may be stained on a cover-slip 

 in Ehrlich-Biondi fluid. 



Pieces of tissue may be stained in haematoxylin and eosin ; they 

 are best cut in paraffin ; sections of frozen tissue can be cut, and 

 stained separately, but there is some danger of losing the epithelium 

 of the villi. The mucous cells can be deeply stained by aqueous or 

 50 p.c. alcohol solutions of methylene blue or of thionin. Formol 

 4 p.c. (one day) and mercuric chloride (one day) are also satisfactory 

 as hardening agents. After hardening in mercuric chloride, excellent 

 results are given by Mallory's triple stain, cp. App. p. 311. 



Sections of rectum if hardened in alcohol are apt to be sticky, on 

 account of the mucin of the mucous cells ; this can be done away 

 with by placing the tissue for a day or two in -5 p.c. chromic acid. 



Peyer's Patches. These are easily recognized as oval patches of the 

 free border of the intestine of a rabbit. In order to show the retiform 

 tissue in them, they may be placed fresh in 5 p.c. ammonium bichro- 

 mate for three to four weeks (kept in alcohol if necessary), cut frozen 

 and shaken up in a test tube, stained with picrocarmine or haema- 

 toxylin and mounted in glycerine, or with any of the double stains 

 given in Less. v. and mounted in balsam. 



The retiform tissue of the follicles will be seen to be continuous 

 with that of the rest of the mucous membrane, but to be rather finer; 



