328 



STOMACH AND INTESTINE. 



^.j^-th of an inch), but also in its meshes being 

 nearly twice as close (or about T ^th to ^^th 

 of an inch). But the two plexuses inosculate 

 so freely, as to be quite continuous with each 

 other at the upper apertures of the tubes. As 



Fig. 253. 



Superficial capillaries of the mucous membrane of the 

 human stomach, from an injected specimen. Mag- 

 nified 70 diameters. 

 a, ridges intervening between the sto mach -tubes ; 



b, capillaries occupying the ridges ; c, orifice of a 



stomach-tube. 



regards the form of the superficial network, it 

 may be stated to correspond exactly with the 

 intervals of the primary tubes. For the 

 ridges which occupy the surface of the organ 

 are all, as it were, moulded upon capillaries, 

 the union of which forms what we may distin- 

 guish as a primary network, that surrounds the 

 aperture of each tube with a capillary loop. 

 In Man,* however, this comparatively simple 

 network is complicated by the addition of 

 other meshes, which lie on either side of it, 

 and just within the orifices of the tubes. In 

 their shape and size, these closely resemble 

 the loops beneath the ridges, and are, indeed, 

 no way distinguishable from them except in 

 their situation. Below, their diameter di- 

 minishes, their loops elongate, and they 

 finally merge into the general network which 

 surrounds the tubes. 



It is from the large capillaries which com- 

 pose the superficial network that the radicles 

 of the veins almost exclusively arise. They 

 begin as small vessels of about -ITOU^ f au 

 inch in diameter ; and by one or two suc- 

 cessive unions of these* and their resulting 

 larger branches, they soon attain a width of 

 about 7 io tn of an inch. They now pass 

 vertically down the intervals between the 

 tubes, to open into the flattened venous plexus 

 which occupies the submticous areolar tissue. 



The general result of this arrangement on 

 the circulation in the stomach seems to be, 

 that the blood which has already traversed 

 the capillaries of its tubes is passed on to its 

 surface. Hence in respect to their situation 

 and size, these superficial capillaries of the 

 gastric mucous membrane offer a distant re- 

 semblance to veins. This fact, as well as their 

 connection, both with small arteries on the 

 one hand, and with confluent capillaries on 



* In many animals the superficial network appears 

 limited to this simpler form ; especially in the cardiac 

 region, Avhere the intervals of the tubes are smaller. 



the other, renders it probable that the velo- 

 city of their contents exceeds that of the 

 blood which circulates in the capillaries of 

 many other tissues. Such a peculiarity would 

 admirably adapt them to that absorptive office 

 which their mere situation on the cavitary 

 surface of the organ indicates as one of their 

 chief functions. 



Changes in the stomach during digestion. 

 The introduction of food into the healthy 

 fasting stomach gives rise to two chief altera- 

 tions in the organ. Its muscular coat is ex- 

 cited* to movement. And, at the same time, 

 its mucous membrane deepens from a pale to a 

 bright pink colour f ; and begins to pour forth 

 a liquid secretion the gastric juice. 



Gastric juice. An inquiry into the cha- 

 racters of the gastric juice is opposed by 

 many difficulties. For it is obvious that the 

 properties of this or any other secretion can 

 only be established from its examination in a 

 state of perfect purity. While the situation 

 and functions of the' stomach are such that, 

 under natural circumstances, its secretion is 

 necessarily mixed with many other substances. 

 It is true that the bile often found J in the 

 stomach during fasting is shut out from its 

 cavity, during digestion, by the closure of the 

 pylorus. But, on the other hand, the saliva, 

 which generally covers the mucous surface of 

 the empty organ, as a thin viscid layer with 

 a superficial alkaline reaction, is swallowed 

 at this period in much larger quantities; while 

 the food itself forms an equally constant 

 impurity. To such less avoidable sources 

 of error are often added the alterations pro- 

 duced by disease in the unhealthy individual, 

 or by putrefaction or digestion in the healthy 

 subject after death. And though even the 

 most careful study of all these circumstances 

 will scarcely explain the discrepancies and 

 contradictions of numerous (and apparently 

 faithful) observers in their accounts of the gas- 

 tric juice, still they evidently constitute con- 

 ditions which, according as they are obviated, 

 or noticed, or neglected, will respectively 

 render any particular observations valid, or 

 comparable, or utterly useless. 



* See ante, p. 312. 



f Beaumont, Op. cit. pp. 94. et seq. 



I See ante, p. 315. 



The above remarks form a key to the following 

 historical summary of the more important observa- 

 tions which have been made on this fluid ; as well as 

 a reason why the author has reduced it to a mere 

 enumeration, such as will not, however, preclude a 

 fuller subsequent reference, where this is required. 



Reaumur, in the year 1752, obtained an artificial 

 digestive fluid from the stomachs of animals by 

 means of sponges attached to strings (Me'm. de 

 1'Academie, 1752. pp. 705. et seq.). About 1780, 

 Spallanzani (Ueber das Verdauungsgeschaeft. Leip- 

 zig, 1785) adopted the same method; and also ex- 

 amined matters which had been vomited. He thus 

 determined the gastric juice to be a neutral, anti- 

 septic solvent. He quotes Scopoli and Gosse to the 

 same effect. Carminati (Untersuchungen ueber die 

 Natur des Magensaftes, 1785) also deduced his 

 results from substances vomited ; and found that it 

 was only the acid fluid secreted after eating which 

 possessed antiseptic and digestive powers. Several 

 observers, however, among whom were Viridet 



