STOMACH AND INTESTINE. 



403 



Finally, the unstriped muscular fibres, and 

 the white and yellow fibrous elements, repeat 

 the ordinary steps seen in the development 

 of these tissues generally. 



ABNORMAL ANATOMY. 



Malformations. The malformations of the 

 digestive canal may be conveniently arranged 

 in three groups: 1. Those which appear 

 to depend on an arrested or deficient de- 

 velopment. 2. Those which are attended by 

 an excess of size. 3. Those which can only 

 be referred to errors of development, the 

 causes of which are unknown ; or to mal- 

 formations of adjacent parts. 



(1.) A deficient development of the whole 

 tube may diminish either its calibre, its length, 

 or both of these dimensions simultaneously. 

 But malformations of this kind are rarely seen, 

 in that marked degree in which alone they can 

 be distinguished from from the differences 

 which doubtless obtain in different indivi- 

 duals. 



Among the results of a local failure of de- 

 velopment, by far the most common is one, 

 which we might expect to be so, both from 

 the history of the evolution of the digestive 

 canal, and from the analogy of malformations 

 in other parts ; namely, the absence of one or 

 both of the terminal orifices of the tube, to- 

 gether with more or less of its adjacent seg- 

 ments. 



Thus the imperforate anus, which is some- 

 times limited to the mere occlusion of the 

 lower orifice of the bowel by a thin mem- 

 brane, is, in other instances, associated with 

 the absence of a variable extent of the rec- 

 tum, and even of the colon, ileum, or jeju- 

 num. In such cases, a cord of more or less 

 dense fibrous tissue generally replaces a vari- 

 able extent of the absent segment of tube. 

 The canal itself is usually dilated above its 

 closed extremity. It may, however, com- 

 municate with the neighbouring urinary or 

 genital cavities ; or it may even open at the 

 umbilicus.* 



The analogous deficiency of the oesopha- 

 gus is of less frequent occurrence than the 

 preceding, and is but very rarely associated 

 with it. Here the pharynx ends below in a 

 blind extremity ; generally forming a pouch, 

 which sometimes communicates anteriorly 

 with the adjacent trachea. The oesophagus 

 below this pouch begins in a similar but nar- 

 rower sac, which is separated from the pha- 

 rynx, either by a membrane, or by a fibrous 

 cord, or by an absolute interval of varying 

 length. 



The deficiency of the stomach occurs 

 chiefly in acephalous monsters. It is some- 

 times accompanied by the absence of the 

 duodenum, or part of the jejunum. 



* In that class of double monsters in which the 

 trunks are distinct below, but united above in the 

 upper part of the belly, a variable length of their 

 two small intestines is sometimes similarly fused 

 into a single tube, which bifurcates above and 

 below. The seat of the lower bifurcation is some- 

 times occupied by a (probably true) diverticulum. 



An incomplete evolution of the remainder 

 of the tube is evinced, either by a local nar- 

 rowness of variable* extent and situation, or 

 by a closure and interruption which (mutatis 

 mutandis) repeat the various grades of this 

 malformation seen in the occluded oesophagus 

 and anus. Or it may exhibit a somewhat 

 analogous tendency of the more complex parts 

 of the canal towards the simply tubular shape. 

 Thus the stomach may be devoid, either of 

 its cardiac sac, or of its pyloric valve; or 

 may present a cylindrical form, precisely like 

 that of the small intestine. Or the valve or 

 pouch of the projecting ccecum, or its vermi- 

 form appendix, may similarly disappear.-f- 

 The maximum of this imperfection renders 

 the whole intestine a narrow cylindrical tube, 

 in which it is impossible to distinguish be- 

 tween the large and small bowel. 



Almost all the foregoing malformations, 

 where excessive, are accompanied by other 

 deformities, which affect the neighbouring or- 

 gans. Thus the deficiency of part of the 

 rectum is a common coincident of the mo- 

 nopodous state, in which the two lower limbs 

 are fused into one. 



(2.) The excess of development to which 

 we may refer the second class of malforma- 

 tions of the digestive canal, consists in an 

 increased length or width of the whole tube, 

 or of any particular part of it. In the latter 

 case, the large intestine, the ccecum, and the 

 stomach are the segments most frequently 

 affected. The other local malformations 

 which we may ascribe to such an excess, are 

 those of subdivision of the canal on the one 

 hand, and the production of diverticula or 

 supplementary tubes on the other. 



Very few of the transverse subdivisions of 

 the tube can, however, be regarded as really 

 belonging to the category of excessive de- 

 velopment. For even where these, as in the 

 stomach, subdivide the cavity of the canal by 

 imperfect septa, into abnormal portions, still 

 the latter generally exhibit a diminished, 

 rather than an increased size 



The longitudinal division of the tube pre- 

 sents us either with a septum, which separates 

 its interior into two channels, that communi- 

 cate again below ; or with a double canal, of 

 variable length and position. 



The double ccecum which has sometimes 

 been observed, might be regarded, either as a 

 bifid or double state of the canal, or as the 



* In rare instances this narrowing is so great as 

 to constitute a virtual occlusion. Thus cases are 

 sometimes met with, in which the whole of the in- 

 testinal canal below the duodenum or jejunum con- 

 stitutes a tube, which retains the formal separation 

 into large and small intestine, but evinces its 

 checked development by its narrow calibre, and by 

 the dilatation or pouch above it, that terminates 

 the normal segment. 



t In some of these latter cases it is probable that 

 the projecting cul-de-sac, which appears to be the 

 coecum only, is in reality the undivided rudiment 

 of both it and the vermiform appendix. 



% Some of these transverse subdivisions of the 

 tube possibly imply a mere arrest of development 

 in the site of the imperfect septum, without any 

 excess of this process in the contiguous parts. 



D D 2 



