498 



MANUAL OF HISTOLOGY. 



Fig. 494. Mouths of tubuiar 

 glands from the colon of the 

 rabbit, with radiating ar- 

 rangement of columnar cells. 



length which varies between 0*4512 and 0'5640 mm. and upwards, 

 the transverse diameter lying between 0-0902 and 0'1505 mm. More- 

 over, they are just as crowded as the gastric and jejunal tubuli, and are 

 found in every part of the large intestine, including the processus vermi- 

 form is. 



They contain a viscid, and at times somewhat fatty mass (fig. 491 and 

 492, b), consisting of nucleated gland cells (measuring 0-0151-0-0226 mm.) 

 made up of granular protoplasm. These present the appearance when seen 

 on the surface of flattened epithelium, from the fact of their being accommo- 

 dated to one another, but are found on section of the gland to be columnar. 

 Here also goblet cells may be encountered 

 (Schuhe). The mouths of these glands are of the 

 ordinary kind, lined with columnar epithelial 

 cells converging towards the lumen (fig. 494). 



The lymphoid follicles are, as a rule, larger 

 than those of the small intestine. Their cupola; 

 project from depressions in the mucous mem- 

 brane. 



We have already remarked that their being 

 crowded together, in the vermiform appendix 

 of the human being, lends to the latter organ a most peculiar appearance 

 ( 255). 



The vascular apparatus of the mucous membrane of the colon presents 

 the same arrangement as that of the gastric mucosa, so that we may refer 

 the reader to fig. 466. 



The lymphatics of the mucous membrane of the colon were until very 



recently quite unknown, although the 

 well-known network of the submucosa 

 had been discovered long before. We 

 are now certain of their existence in the 

 mucous membrane of phytophagous and 

 carnivorous animals, and it is highly 

 probable thai they are not absent in 

 man. 



Though the surface of the colon is, as 

 a rule, quite smooth, we find its upper 

 fourth in the rabbit thickly studded with 

 broad projections comparable to the in- 

 testinal villi. 



These papillae, however (fig. 495), in 

 contradistinction to the villi of the small 

 intestine, are just as densely crowded 

 with tubular glands as the other por- 

 tions of the mucous membrane of the 

 colon. ' 



In the axial portion of these pro- 

 minences one or more blind lymphatic 

 radicles are to be seen (/, g\ precisely similar to those of the small intes- 

 tine. Descending perpendicularly, and twined about by a vascular net- 

 work (a-d), they pass into the loose mesh-work of the submucous 

 lymphatic vessels. In other animals the smooth mucous membrane of 

 the colon is traversed partly by perpendicular caecal canals, and partly by 

 a wide-meshed net-work. These lymphatic vessels, which do not by any 



Fig 495. Papilla from the colon of a rabbit, 

 in vertical section, a, arterial; 6, venous 

 twig of the submucosa; c, capillary net- 

 work ; d, descending venous twig ; e, hori- 

 zontal lymphatic vessel ensheathing an 

 artery ; /, lymph canal in the axis ; g, 

 caecal extremity of the same. 



