146 THE ESSENTIALS OF HISTOLOGY 



LESSONS XXIX. AND XXX. 



STRUCTURE OF THE INTES TINE. 



LESSON XXIX. 



1. SECTIONS of the duodenum or jejunum vertical to the surface. The 

 tissue is to be stained with logwood or borax-carmine 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. From the same portion of the intestine, sections parallel to the 

 surface, 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 will be necessary to employ the creosote- 

 shellac method of mounting the sections (see Appendix). 



In this preparation sketch the transverse section of a villus. 



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 lym- 

 phatic 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 rat three or four hours 

 after feeding it with fat meat. Put a very small piece of the mucous mem- 

 brane of the intestine into osmic acid (0*5 per cent.) and another piece into 

 chromic acid (0*2 per cent.) containing a few drops of osmic acid solution. 

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

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

 may be then placed in alcohol. The piece in chromic and osmic acid may 

 also after two or three days be placed in alcohol. When hardened and de- 

 hydrated in this, the pieces of tissue are embedded in paraffin, and sections 

 are made and mounted by the shellac-creosote process. 



LESSON XXX. 



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 

 Farrant's solution. It will generally be found that portions of the nervous 

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

 easily be studied. 



From the remainder of the piece of intestine tear off with forceps the 



