STRUCTURE OF THE INTESTINE. 173 



LESSONS XXXI. AND XXXII. 



STRUCTURE OF THE INTESTINE. 

 LESSON XXXI. 



1. SECTIONS of the duodenum and jejunum vertical to the surface. The tissue 

 is to be stained with hsematoxylin and the sections mounted in Canada balsam. 

 The general arrangement and structure of the intestinal wall is to be studied 

 in these sections. 



Make a general sketch under the low power and carefully sketch part of a 

 villus under the high power. 



2. Sections parallel to the surface of the intestine, and therefore across the 

 long axis of the villi and glands of the mucous membrane. In order to keep 

 the sections of the villi together so that they are not lost in the mounting, it 

 is necessary either to embed in celloidin or, if paraffin be used, to employ an 

 adhesive method of mounting (see Appendix). 



In this preparation sketch the transverse section of a villus and of a crypt 

 of Lieberkiilm. 



3. Transverse vertical sections of the ileum passing through a Peyer's patch. 

 Observe the nodules of lymphoid tissue which constitute the patch and which 

 extend into the submucous tissue. Notice also the sinus-like lymphatic or 

 lacteal vessel which encircles the base of each nodule. Make a general sketch 

 under a low power. 



4. To study the process of fat-absorption, kill a mammal, e.g. rat, three or 

 four hours after feeding it with a little fat, or a frog two or three days after 

 feeding with lard. Put a very small shred of the mucous membrane of the 

 intestine into osmic acid (0'5 per cent.) and another piece into a mixture of 2 

 parts Muller's fluid and 1 part osmic acid solution (1 per cent.). After 

 forty-eight hours teased preparations may be made from the osmic acid 

 preparation, in the same manner as directed in Lesson VII., sec. 2 ; the rest 

 may be then placed in 70 per cent, alcohol. The piece in. Miiller and osmic 

 acid may be left for ten days or more in the fluid. When hardened, the 

 pieces of tissue are soaked in gum, and sections made with a freezing 

 microtome and mounted in glycerine. The sections must not be passed 

 through any fluid which dissolves fat. 





LESSON XXXII. 



1. SECTIONS of small intestine the blood-vessels of which have been injected. 

 Notice the arrangement of the vessels in the several layers. Sketch carefully 

 the vascular network of a villus. 



2. From a piece of intestine which has been stained with chloride of gold 

 tear off broad strips of the longitudinal muscular coat, and mount them in 

 glycerine. It will generally be found that portions of the nervous plexus of 

 Auerbach remain adherent to the strips, and the plexus can in this way easily 

 be studied. 



