E. THE SMALL INTESTINE, BY E. VERSON. 563 



acetic acid and ninety -nine of distilled water, or in a solution 

 containing 32*5 per cent, of liquor potassse (Moleschott), it may 

 easily, after the lapse of a few minutes, be broken up into fibre 

 cells which, especially after the action of the acetic acid, exhibit 

 a distinct nucleus, with one or two nucleoli. The muscle cells 

 appear smooth, or sometimes angularly folded, and are seldom 

 longer than 0'225 of a millimeter, and broader than O005 of a 

 millimeter. No differences can be discerned in the size of the 

 elements forming the longitudinal and circular fibrous layers 

 respectively. In other Mammals, however, they may be both 

 longer and broader, as is remarkably the case also in the 

 Amphibia ; those of the Proteus and Salamander being surpass- 

 ingly large. 



The several muscular fibres constituting the muscular tunic 

 of the intestine are held together by a kind of cement. Their 

 larger fasciculi are enclosed by bands of connective tissue, which 

 divide the muscular substance when seen in cross section partly 

 into numerous areas of equal size, and partly into larger seg- 

 ments, which embrace the whole thickness of the muscular 

 tunic, 



6. Mucous MEMBRANE. 



The mucous membrane constitutes the innermost tube, and 

 exhibits peculiar elevations which project in the form of folds 

 and villous processes into the lumen of the intestine. 



The folds termed also the valvulse conniventes of Kerkrin- 

 gius run more or less at right angles to the long axis of the 

 intestine, and are either parallel to each other, or unite at acute 

 angles, and always become separated by wider intervals towards 

 the lower part of the small intestine. 



The folds of Kerkringius are commonly regarded as persis- 

 tent formations, because the muscular tunic does not enter 

 into their interior. Nevertheless certain parts of the small 

 intestine occur in children, where the muscular coat presents 

 alternate contractions and relaxations. In the former these 

 folds of the mucous membrane are sharply defined and pro- 

 minent ; whilst opposite the latter the membrane is perfectly 

 smooth, thus affording strong evidence that the folds in ques- 



