STOMACH AND INTESTINE. 



361 



extremities, on the bulging surface of the fol- 

 licle. 



Racemose, or Brunn's glands. The re- 

 maining constituent of the compound intes- 

 tinal membrane is one which, unlike all the 

 preceding minute organs, is limited to a very 

 small segment of the canal. It consists of a 

 number of highly ramified tubes, which are 

 usually termed the glands of Brunn, but 

 might preferably be named the racemose or 

 duodenal glands. These glands occupy that 

 upper part of the small intestine already 

 distinguished as the duodenum ; of which 

 segment they are thus, as it were, the natural 

 index, or the characteristic structure. 



The racemose glands are small " conglo- 

 bate " masses; which in their size, structure, 

 and position, closely resemble those accessory 

 salivary organs that stud various parts of the 

 mucous membrane lining the cavity of the 

 mouth. Like these " labial" and " buccal " 

 glands, they occupy the sub-mucous areolar 

 tissue : and are therefore best examined by 

 pinning out a piece of the duodenum on some 

 flat surface, with its mucous side downwards, 

 and then carefully removing the serous and 

 muscula. coats. Such a dissection easily ex- 

 poses them, as small roundish white granules 

 of about the size of a millet seed. 



They vary considerably in size and arrange- 

 ment. Immediately beyond the pylorus, they 

 are of one-tenth to one-eighth of an inch 

 in diameter; and are present in such num- 

 bers, as to form what is almost a glandular 

 layer around this part of the intestine. But 

 lower down in the duodenum, their size 

 dwindles to one-half or one-third of the 

 above : and their scattered grains gradually 

 become more sparing in number; until, shortly 

 before the termination of its inferior transverse 

 portion, they cease altogether. 



On tracing out the structure of an isolated 

 duodenal gland under the microscope, it is 

 seen to consist of numerous lobules; which 

 are aggregated into a single mass (c c,jig.212.), 

 by an enveloping layer of fibrous tissue. And 

 on applying a still higher magnifying power, 

 each of these lobules may be again resolved 

 into smaller ones, which resemble a bunch of 

 grapes, and constitute the true or ultimate acini 

 of the gland. As seen in situ, these vesicles 

 have a globular or slightly polyhedral form; 

 and a diameter which is about -g^th to ^^t\i 

 (on an average, ^io tn ) f an Ulcn - ^nt when 

 separated from each other, they often exhibit 

 more irregular shapes (d,fig. 273.). They are 

 the terminal dilatations of tubes, which are 

 themselves about two-thirds of this size. On 

 tracing these minute tubes towards the general 

 mucous surface, they will be found uniting with 

 other similar ones, to form larger ducts. The 

 successive union of these with other ducts 

 formed in the same way, and of these larger 

 ducts with their neighbours, gradually causes 

 all their cavities to converge into a single canal 

 of outlet, which is the proper efferent duct of 

 the gland. This duct now passes between the 

 intestinal tubes before described, to open on 

 the free surface of the intestine, in the depres- 



sions which intervene between the rudimen- 

 tary villi present here. The valvulae conni- 



Fis. 272. 





Racemose or duodenal gland, as seen in a vertical 

 section of the duodenum. Magnified 40 diameters. 



a, intestinal tubes; b, muscular stratum of the 

 mucous membrane ; c, c, acini of the duodenal gland, 

 which occupies the submucous areolar tissue ; d, 

 transverse layer of the muscular coat ; e, longitudi- 

 nal layer of the muscular coat ; f, peritoneal tunic 

 of the bowel. 



ventes are not permeated by any such ducts. 

 But in all other parts of its surface, the 

 general mucous membrane is pretty evenly 



Fig. 273. 



Diagram of the arangement of the lobules of a duode- 

 nal (jland. 



a, duct of the lobule; b, collateral branch of this 

 duct ; c, the acini around such a duct in situ ; d, the 

 same separated, and the duct unfolded. 



studded by their apertures, two or more some- 

 times passing through it in company with each 

 other. 



Hence each of these glands may be briefly 

 described as a tube, which branches repeatedly, 

 and ends in very minute canals, with some- 

 what vesicular extremities. 



The whole of this involution of mucous 

 membrane is composed of the usual elements ; 

 namelv, limitary membrane and epithelium. 

 The former constituent offers no peculiarity 

 worthy of note. The latter consists of a single 

 tesselated layer of cells. These have a poly- 

 gonal and slightly flattened shape, which some- 



