ANATOMY OF SEROUS MEMBRANES. 21 



he recognised by its colour. It happened 1o the same anatomist 

 to find in two bodies, where there had been an effusion of blood 

 into the thorax, the absorbents of the lungs gorged with blood. 

 This faculty of absorption may sometimes be proved to continue 

 for some hours after death, by keeping an animal in a warm 

 bath. Mascagni asserts, that he has witnessed its continuance 

 for fifteen, thirty, and even for forty-eight hours; it is not im- 

 probable, however, that there was some illusion in these in- 

 stances. 



It is more than probable that the serous membranes are en- 

 tirely deprived of red blood vessels; the latter unquestionably ex- 

 ist, in great numbers, on the exterior surface, where they creep 

 through the cellular substance, but they may be removed with 

 a scalpel without affecting the continuity of these membranes. 

 Again, where these membranes are free and unconnected on both 

 surfaces, as in some parts of the tunica arachnoidea, there is no 

 appearance of red blood vessels. In hernial protrusions, where 

 there is a considerable prolapse of peritoneum, the blood vessels 

 which are found abundantly about the neck of the sac do not fol- 

 low the course of the protrusion. Unquestionably some com- 

 munication exists between the arterial system and the serous 

 membranes, as proved by exhalation and morbid phenomena, 

 but the mode is not well ascertained. 



In common hernia and in dropsy, the serous membranes be- 

 come more thick: from my dissections I am inclined to think, 

 that this change is not so great as is generally allowed; for most 

 frequently, by a careful removal of the exterior cellular sub- 

 stance, they have been restored to their primitive condition. In 

 other cases, as in large umbilical hernias, they are so much at- 

 tenuated as to be found with difficulty. 



The power of extension which these membranes possess, is 

 strikingly marked in dropsical effusions, in the development of 

 tumours, and in pregnancy; but much of this apparent quality 

 is derived from their mode of attachment to adjacent -parts, 

 whereby they are drawn from one surface to cover another. 

 This happens daily where the peritoneum is drawn from the 

 lower part of the abdomen to cover the bladder in the distentions 

 of the latter; in pregnancy, where it is drawn upon the growing 

 uterus from all the neighbouring parts; and in the distentions of 

 the stomach by food or flatus, where it is drawn up from the 



