2S2 



PRACTICAL HISTOLOGY. 



[xxv 



ADDITIONAL EXERCISES. 



13. T.S. Villus. Stain a hardened mucous membrane (with villi) of a dog 

 or cat "in bulk" in borax-carmine or Kleinenberg's logwood, embed and cut 

 T.S. in paraffin, fix on a slide, remove the paraffin with turpentine, clarify 

 with clove-oil, and mount in balsam. Many of the villi will be cut obliquely. 

 (H) Observe the lacteal (L) in the centre, and round it the structure of the 

 stroma of the villus, with several groups of non-striped muscle-cells (m) close 

 to and surrounding the lacteal. In some animals (dog) there is a double row 

 of these smooth muscles (fig. 272). The capillaries immediately under the 



epithelium (c), the smooth muscular 

 fibres parallel to the lacteal, and the 

 stroma composed of anastomosing 

 fine trabeculae with parenchymatous 

 cells and leucocytes make up the 

 elements present in the core of a 

 villus. 



Great differences exist in the rela- 

 tive size of the stroma and lacteal in 

 villi. In the dog and cat the lacteal 

 is relatively small, and the stroma 

 abundant ; in the rabbit the lacteal 

 is very large, and the stroma scanty. 

 14. Non-Striped Muscle in Villi. 

 The method of Kultschitzky enables 

 the course of the fibres to be more 

 clearly traced. Harden (for twenty- 

 four hours) a piece of dog's small in- 

 testine in the following fluid : A 

 saturated solution of potassic bichro- 

 mate and copper sulphate in 50 



FIG. 272. T.S. Villus (Dog). L. Lacteal 

 m. Muscle ; c. Capillaries, x 400. 



cent, alcohol (in the dark), to which, immediately before using, is added 

 5-6 drops (to 100 cc.) of acetic acid. The preparation and fluid must be kept 

 in the dark. Complete the hardening in absolute alcohol. Make sections, 

 and stain them in acid chloral-hydrate carmine, which is made as follows : 

 Chloral hydrate, 10 grams; hydrochloric acid (2 per cent.), 100 cc. Add to 

 this dry carmine (.75 to 1.5 gram), according to the strength of stain desired. 

 Boil for one and a half hours, preventing evaporation by means of a cooling 

 apparatus. Allow it to cool and filter. If the preparations stained with this 

 dye be washed in 2 per cent, alum, the nuclei and other tissues become violet. 



Sections stained thus show the course of the smooth muscle -from the 

 muscularis mucoscs obliquely between Lieberkiihn's glands into the villi, where 

 they are arranged in several bundles near the lacteal. They curve as they 

 ascend in the villus, the concavity looking outwards, and are fixed or inserted 

 close under the epithelium. They pass quite to the apex of the villus, becom- 

 ing thinner as they go, where they each split up into a pencil of fibres, the 

 fibres being inserted close under the epithelium. 



15. Heidenhain's Method. Harden small pieces of the small intestine, 

 e.g., dog or cat (24 hours), in a .5 solution of common salt saturated with 

 mercuric chloride. Place it for twenty-four hours in alcohol 80, 90, and 95 

 per cent., and finally in absolute alcohol. Saturate with xylol, embed in 

 paraffin, and cut thin sections, which are fixed on a slide with a "fixative." 

 After the paraffin has been got rid of by turpentine or xylol, and the turpen- 

 tine displaced by alcohol, the sections are stained on the slide with Ehrlich- 



