STOMACH AND INTESTINE. 



321 



Their diameter is about ^irg-th of an inch, 

 but is also increased towards the pylorus. 

 Tims their length has to their breadth a pro- 



Stomach-tube from the middle of the human stomach. 

 Magnified \ 40 diameters. 



a, wall of the tube, lined with large oval nu- 

 cleated cells ; b, the same oval cells isolated, and 

 magnified 800 diameters ; c, nucleated cells of co- 

 lumnar epithelium, occupying the upper parts of 

 the tubes, and the intervening ridges ; d, blind ex- 

 tremity of the tube. 



portion of about 10 to 1. Their form fre- 

 quently so far deviates from that of a simple 

 cylinder as to present slight constrictions or 

 undulations. And occasionally they even 

 exhibit a kind of caecal pouch or blind offset 

 of greater or less length. These pouches 

 usually spring from the lower extremities of 

 the tubes, which generally have a somewhat 

 increased diameter in their neighbourhood.* 

 But with these exceptions, the gastric tubes 

 form simple, straight cylinders, which only 

 widen where they open on the inner surface 

 or cavity of the stomach. -j- 



* These appearances are generally more marked 

 in the separated fragments of a specimen, or on its 

 exposed edges and surfaces, and are certainly often 

 absent. From this and other reasons I have 

 long entertained the suspicion that they are chiefly 

 due to mechanical violence. 



) A widening of diameter which obviously cannot 

 exceed the thickness of the matrix around each 

 tube, and may therefore be easily estimated from 

 the amount of this latter tissue seen in looking at 

 any vertical section of the mucous membrane in sitft. 



Sujtj). 



The limitary or basement membraite which 

 forms these tubes precisely resembles this 

 delicate homogeneous layer of the mucous 

 structures generally, except perhaps in the 

 fact of its possessing an even greater tenuity. 

 It is usually seen only as a dark outline, 

 bounding some part of a tube that happens to 

 have been isolated entire. Rarely, however, 

 it may be identified as a delicate, floating, and 

 collapsed fold, which, on the addition of a 

 dilute alkali, first swells up, and then alto- 

 gether disappears. On the ridges which 

 unite the tops of the tubes it is quite im- 

 possible to separate it from the subjacent 

 structures; an intimate adhesion which forms 

 a striking contrast to the ease with which we 

 can often isolate the tubes themselves. 



The contents of these tubes appear to be every- 

 where alike. In the upper fourth or fifth of their 

 length, they contain a single layer of columnar 

 epithelium (c,fig. 246.). Seen as isolated cells, 

 the particles of this epithelium have a cylin- 

 drical shape, and enclose a very distinct nu- 

 cleus near their attached extremity. But when 

 we look at them in their natural situation, 

 from the free side of the mucous membrane, 

 we see that they are rather hexagonal prisms 

 than cylinders ; and contain nuclei, which 

 appear to lie so near to their lower ends, as to 

 be separated from the basement membrane by 

 little more than by the cell-wall at this part. 

 The remainder of the tube is occupied and 

 under normal* circumstances appears to be 

 filled by oval or somewhat angular cells 

 (a d, and b, fig, 246.) of considerable size. The 

 largest of these oval cells are about -2V7r tn f 

 an inch in diameter. They have a more or less 

 distinct membranous wall. The nucleus they 

 contain is usually in contact with that side of 

 their parietes which is attached to the base- 

 ment membrane of the tube ; and it some- 

 times exhibits a nucleolus. Their contents 

 are finely granular, with here and there re- 

 fractile dots that have a close resemblance to 

 oil globules. And the author has been able 

 to establish the fact, that a large proportion 

 of these cells enclose, beside the above granu- 

 lar material, numerous (5 15) pale, flat, and 

 extremely delicate cytoblasts. Whether the 

 centre of the layer formed by these cells 

 constitutes a distinct calibre or cavity of 

 the tube, or whether it is merely an in- 

 terval occupied by granules or cytoblasts 

 he is unable at present to decide. 



As has already been hinted, the gastric mu- 

 cous membrane is distinguished from most 

 other parts of the body, not only by the great 

 delicacy of its structure, but by the com- 

 plexity of its arrangement; and above all, by 

 the remarkable facility and rapidity with 

 which it undergoes disorganization and de- 



* It is very common to find portions of the tubes 

 quite devoid of these cells, and occupied by a gra- 

 nular substance, with nuclei and cytoblasts in vary- 

 ing proportion. But I believe that this appearance, 

 which is especially frequent in the blind ends of the 

 tubes, is generally the result of mechanical injury 

 of the original cells. (Compare p. 824.) 



