180 GENERAL ANATOMY. 



plied to these. They are subject, more than the other, to some 

 primitive vices of conformation, as unnatural openings, ob- 

 served in some cases of monstrosity, of which they all may 

 present examples, as well as the prolongations or appendages 

 which envelop congenital hernias and other displacements. 



235. Accidental hernias are also accompanied by an altera- 

 tion in the form of the splanchnic serous membranes; displaced 

 parts are almost universally enveloped by a hernia! sac: this 

 sac is formed by the serous membrane which lines their pa- 

 rietes, and which the viscera, in being displaced, push before 

 them. 



236. Dropsy, inflammation and its effects, false membranes, 

 adhesions, accidental productions, either analogous, or morbid, 

 are more common in the splanchnic serous membranes, than 

 in the other species, and still more common among some of 

 their own number than in others. 



237. Although the splanchnic serous membranes, form a 

 tolerably natural group, they still present differences which 

 belong to special anatomy; the arachnoid besides, differs much 

 from the others. It has the same conformation as the others, 

 but its consistence is soft, its tenuity extreme, and its texture 

 it is impossible to determine; it seems homogeneous; no ves- 

 sels are to be found in it, not even in a diseased state. The 

 greater part of the morbid phenomena attributed to it, takes 

 place in the subjacent tissue of the pia-mater; it seems, in fact, 

 to form a genus by itself. 



