SMALL INTESTINE. 73 



Small Intestine. For the structure of villi. The section 

 contains L. and T.S. mounted side by side. (p. 3, inj., s. 22 & 24, 

 c. P., m. B.) Recognise (//) the single layer of columnar cells 

 on the surface, together with their end plates. This layer 

 rests on a well-defined surface, formed by the adenoid reticulum 

 which constitutes the supporting framework of the villus. 

 Internal to this find blood capillaries (probably quite invisible 

 being collapsed) and next a zone of muscular strands from 

 the muse, mucosse. In the middle the central lacteal may be 

 observed as a partially open cleft. 



Small intestine for fat absorption. Frog. (The animal is 

 fed upon a piece of bacon fat or some lard and is killed four 

 or five hours afterwards. The intestine is cut out and small 

 pieces are quickly placed in 1 p-c- osmic acid for 48 hours, 

 p. absolute alcohol with eosin, c. P., m. B.) (H) Find the 

 columnar cells loaded with small fat granules near their free 

 ends which become larger towards the nucleus. Is there any 

 fat to be seen in the substance of the end plate ? Much fat 

 is recognisable in the subjacent tissue of the villus. 



Small intestine of rabbit, for Auerbach's ftlwn*. 



A loop of small intestine is washed out with normal saline and is 

 then tied at one end and filled with Ranvier's boiled gold solution 

 (28). The fluid is kept in by a second ligature and the whole is 

 immersed in gold solution for 45 minutes. The <_L\\\ is then, cut into 

 short lengths, is rinsed in distilled water, and is traust'erred to '20 i'- - formic 

 acid for 24 hours, or longer, until the gold is ivdueed, which will be 

 recognised by the uniform reddish violet colouration. Place- in glycerin 

 with a little formic acid until required. 



A -piece of the gut is laid open by a longitudinal incision and laid 

 peritoneal surface downwards upon a slide. The mueo<a is next scraped 

 off with the flat of a needle so as to leave only the muscular coat, m. 

 in glycerin containing a little formic acid. 



(L) The plexus will be recognised as ;i large somewhat square 

 meshed network lying between the 1 avers of the muscular 



