20 ORGANS OF DIGESTION. 



duce the same results when applied to the secretion from the se- 

 rous membranes. 



The system of serous membranes has been considered by Bi- 

 chat, and others, as only a modification of cellular membrane, for 

 thejfollowing reasons. The inflation of air into the cellular tis- 

 sue subjacent to them, reduces them to the form of cellular sub- 

 stance. Protracted maceration produces the same effects with 

 more certainty and precision. JiVhen cellular membrane is in- 

 flated, the parietes of the distended cells resemble strongly the 

 finest parts of the serous system, as the arachnoid membrane. 

 There is an identity of functions and of affections, for they are 

 both continually engaged in the great work of exhalation and ab- 

 sorption, and suffer in the same way from dropsical effusion, with 

 the only difference that the latter is more amassed in the one 

 than in the other. My own experience goes to prove, that drop- 

 sy very seldom manifests itself, to any extent, in the cellular tis- 

 sue without also going to the serous cavities, and the reverse. 

 The serous membranes are also of a uniform texture, like cellular 

 substance, and present no appearance of a fibrous matter. 



The serous membranes are furnished with a great abundance 

 of exhalent pores, and of absorbents, which carry on their func- 

 tions with great activity. They, when healthy, receive only the 

 colourless part of the blood, whence the uniform transparency of 

 these membranes. The existence of exhalent pores, is proved 

 by strangulating a piece of intestine with a ligature for thirty-six 

 or forty-eight hours, when they become evident, by dilating them- 

 selves so as to receive red blood. A fine coloured injection pro- 

 duces the same result; and also moistens, by the escape of its wa- 

 tery particles, the surface of the intestine, by a very fine halitus 

 or dew. The intestine of a living animal, if wiped perfectly dry, 

 will, after the same way, soon present another coat of serosity on 

 its surface. The existence of absorbents to a great extent in 

 them, may also be equally well proved, as they very readily re- 

 ceive a mercurial injection, which diffuses itself over their whole 

 surface, and causes them to have the appearance of being formed 

 entirely of such vessels. The readiness with which fluid effused 

 into their cavities is taken up, is another proof of the same. Bi- 

 chat once saw them distended with air in a man who had be- 

 come emphysematous from poisoning. Mascagni has frequently 

 found them distended with the fluid of dropsical collections, which 



