24 THE AMERICAN MONTHLY [February, 



3. Between the mucous membrane and the circular muscle layer, and not 

 the latter (1. m.), a portion deeply stained; it is the loitgitudinal muscle 

 layer. 



4. Next the mucous membrane (s. m.) a space, which is largely open, 

 but sparingly occupied with branching pieces of stained material ; these 

 are the supporting or connective tissue portion of the organ called the sub- 

 mucous lay e7-. 



5. In addition to the parts mentioned and not shown in figure i, though dis- 

 tinguishable on the section close to the mucous membrane, scattered through 

 the sub-mucous layer, are muscles which move the mucous layer — the muscles 

 of the mticous membrane. 



In addition to the cross-section figured in i , it is necessary to examine lon- 

 gitudinal sections passing through the centre of the intestine called ' radical 

 sections,' and comjoare them with the transversal sections, identifying in the 

 latter all of the 5 parts already discovered by an examination of the transverse 

 section. Such a section is represented in both figure 2 and figure 4, though 

 on a very much larger scale than that employed in figure i . When the results 

 of these two exaininations are put together, the combined result will be some- 

 what as follows : — 



1. Mucous membrane. — The lining next to the cavity of the intestine is 

 a continuous, unbroken sheet, which is to be found in all sections longitudinal 

 or transverse next the cavity. It is not a smooth lining, but is everywhere 

 thrown in folds which, further, do not all of them run in any definite direc- 

 tion, but are extreme, irregular in both depth and direction. This fact is 

 shown by the sections in any of which such huge corrugations, as are shown 

 in figure 2, may be noticed. It is seen, in addition, that the mucous lining 

 does not follow the contour of the circular muscle layer, except in a very rough 

 way, its bendings and foldings being entirely independent of the outline of the 

 circular muscle layer. The extent and arrangement of this membrane being 

 thus determined, we ma}' inspect it somewhat more closely, discovering a 

 number of difierent component parts which, together, form the broad band. 

 This band is recognized by its color, and the disposition in it of deeply colored 

 red nuclei, and traces of the elements, the cells^ of the mucous membrane. 

 The examination will show further {c) a transparent, very thin layer upon 

 the outer ends of the cells which compose the mucous membrane, the ctiticle. 



2. The circular muscle layer is seen from the longitudinal and trans- 

 verse sections to be a very thin coat which binds together all the remaining 

 parts of the intestine. It is a coat of rather even thickness, and, even with a 

 low power, its histological structure can, though with difficulty, be seen. It 

 is found present through the entire length of the intestine, in longitudinal sec- 

 tions, as in figure 4, at c. m. ; it is cut across and presents an appearance 

 very unlike that of the cross-sections of the intestine. 



3. The longitudinal muscle layer appears very diflerently in cross and 

 longitudinal sec1,ions, but. of course, is found in the same situation in each, 

 namely, next the circular layers and adhering closely to it. It is seen to be 

 very much greater in extent, reaching across one-half the thickness of the 

 intestine wall, and the radial sections show why the layer is called longitudhial 

 (see fig. 4), its various elements having very distinctly a distribution parallel 

 with the long axis of the intestine. The fine histological structure of these 

 parts will claim attention presently, but for the present let me merely call 

 attention to the general anatomical feature, the relation of the various com- 

 ponent parts of this complex organ — the intestine. The longitudinal muscu- 

 lar layer is not definitely bounded by an even surface upon the side toward 

 the mucous membrane, but is in places apparently ' frayed out' by bands 

 which stretch from it into the sub-mucous coat, as may be seen in both the 



