STOMACH AND INTESTINE. 



409 



first or " active " form of congestion may ge- 

 nerally be distinguished from the latter or 

 " passive " variety. The active hyperaemia 

 is immediately attended by an enlargement in 

 the calibre of the afferent arteries; the pas- 

 sive, by a diminution in that of the efferent 

 veins. Again, the former usually has the 

 colour of a tolerably scarlet or arterial blood ; 

 the latter, that of a darker and more venons 

 fluid. Lastly, the active form affects chiefly 

 the minute arterial branches and the capil- 

 laries ; the passive is most prominent in the 

 veins which come from these ultimate vessels. 

 The hyperaemia of enteritis and of cirrhosis 

 respectively, might well illustrate this con- 

 trast. 



Amongst the varieties of hyperaemia, we 

 may notice a more or less complete limitation 

 of this state to the capillaries of particular 

 tissues. Thus the microscope sometimes 

 reveals a congestion of the gastric or intestinal 

 mucous membrane, that specially engages 

 those capillaries which surround the mouths 

 of its tubes. In other instances, their blind 

 extremities exhibit a similar state of injection. 

 The exact cause of such partial hyperaemia is 

 scarcely known. But the first of these va- 

 rieties appears to be generally connected 

 with a very limited amount of congestion. In 

 accordance with this fact, it seems frequently 

 to occur during or after death. 



Hcemorrhage. Haemorrhage is by no means 

 an unusual morbid occurrence in the digestive 

 canal. 



Of course, the mere presence of blood in 

 some part of the alimentary tube, affords no 

 proof that it has been derived from the vessels 

 which occupy its walls. The blood which 

 reaches the pharynx in cases of haemoptysis, 

 or of lesions of the nose, mouth, or pharynx, 

 is often swallowed, and is thus introduced 

 into the stomach or bowels. In like manner, 

 blood effused into the ducts of the liver or 

 pancreas, may be carried onwards through 

 these tubes, so as to simulate haemorrhage 

 into the intestinal canal ; or the blood ex- 

 travasated into cysts, abscesses, and tumours, 

 may find its way, through some abnormal 

 opening, into the cavity of the bowels. 



It was formerly supposed that, in many 

 cases of haemorrhage, the walls of the vessels 

 remained uninjured ; or, at least, unaffected 

 by any definite solution of continuity : the 

 blood being set free from its channels by 

 " exhalation " through their porous walls. 

 But we now know that this doctrine is in- 

 correct ; that the walls of even the finest 

 capillaries have no pores of appreciable mag- 

 nitude, such as are necessary for the transit 

 of blood-corpuscles: and hence that the 

 "extravasation" of these structures is, ijiso 

 facto, a proof that some blood-vessel has been 

 ruptured. That, amongst the myriads of 

 these minute tubes present, we often fail to 

 detect the exact seat of the lesion, need, of 

 course, little surprise us. 



The frequency with which haemorrhage oc- 

 curs in the digestive canal, seems related chiefly 

 to the number and delicacy of its vessels, to 



the nature of its tissues, and to the mode in 

 which these structures are arranged with 

 respect to each other. Amongst such pre- 

 disposing causes we may especially notice, that 

 the greater part of its large vascular supply 

 breaks up into a vast and dense network of 

 capillaries, which is placed in the closest 

 proximity to the free surface of the mucous 

 membrane. While the latter structure not 

 only has a consistence which disease can 

 readily reduce below what is necessary for 

 the mechanical support of these delicate ves- 

 sels ; but is the constant seat of muscular 

 movements, which agitate it in almost every 

 conceivable plane. 



The extravasatecl blood may either occupy 

 the interstices of the intestinal tissues, or 

 may make its way into the cavity of the 

 canal. 



The former case is much the less frequent 

 of the two. As we might inter from the ana- 

 tomy of the tube, the areolar tissue around 

 the submucous stratum of vessels is by far 

 the most frequent situation of such intersti- 

 tial haemorrhage. 



The blood which is effused by haemorrhage 

 into the cavity of the tube itself may be either 

 fluid or coagulated, arterial or venous, pure 

 or mixed, changed or unchanged. With respect 

 to the latter alternative, we may point out, 

 that blood effused into the digestive canal 

 not only becomes mingled with the various 

 ingesta and secretions which may chance to 

 be present, but gradual!}' undergoes a kind of 

 digestive process, that often has the effect of 

 greatly modifying its colour and consistence. 

 Hence, where the extravasatecl blood has been 

 sufficiently exposed to this action, it will gene- 

 rally be found to have acquired adark,grumous, 

 or even black colour, and a peculiar tarry or 

 almost pultaceous consistence. While con- 

 versely, if the effusion be excessive in quan- 

 tity, or recent in occurrence, it may be pure 

 enough to testify to its arterial or venous 

 source. A small quantity of blood thus altered 

 by digestion sometimes simulates the colour 

 and appearance of inspissated bile. But by 

 diluting the sanguineous mass with water, its 

 dark-purple or blackish hue may be at once 

 distinguished from the rich yellow colour 

 which is proper to the biliary secretion. And 

 a microscopic examination would, of course, 

 assist (or even replace) this means of diagnosis. 



The nature of these intestinal haemorrhages 

 is very various. Apart from mechanical 

 injuries of the canal by foreign bodies ap- 

 plied to it from within or from without, we 

 may classify (but scarcely separate) them 

 into haemorrhages from two sources: from 

 abnormal states of the vessels themselves ; 

 and from diseased conditions of the con- 



tiguous tissues. 



As examples of the former variety, we may 

 adduce the haemorrhage produced by the rup- 

 ture of an atheromatous artery ; or the ex- 

 travasation which occurs in cirrhosis from 

 obstruction and distention of the portal veins. 



The haemorrhage of inflammation, of ulcer- 

 ation, of atony, may be referred to the second 



