CHAP. II.] MEMBRANES. 87 



Of these coverings the most universally dispersed 

 over the frame, those which occupy, defend, or em- 

 brace every part, are the membranes. As well 

 behind as before the midriff, not only inside, but 

 on the outside, and every part of the animal, are 

 these skinny films placed, for the purpose, 1st, of 

 keeping those parts which they encompass in a com- 

 pact state ; 2d, to secrete a fluid more or less oily for 

 their protection (see sect. 21.) ; and, 3d, to prevent 

 those parts from rubbing against and injuring each 

 other, or adhering together. The better to accom- 

 plish these purposes, they are admirably calculated 

 for the secretion of a fluid, as we observed before 

 (sect. 20.) ; but, whenever the property of secreting 

 such fluid is suspended, then disease begins, and 

 according as the secretion may prevail, being either 

 too little or too much, will be the kind and quantity 

 of disease. Hereupon may be calculated the im- 

 portance they hold in carrying on the animal system, 

 as was said higher up. 



Membranes. — To appearance they are nearly 

 transparent, web-like, and of a strong texture ; some 

 are simply film, having more or less of feeling ac- 

 cording to their uses, and are those which, being 

 interposed between one organ, or part, and another, 

 prevent the interruption which would otherwise 

 ensue ; as the midriff, for instance, which we have 

 just above adverted to (see also sect. 31 and 35.), 

 which is the thickest of all, or the loose membrane 



all surgical operations, these, with the skin, are termed the integu- 

 ments, or coverings of the bones. 



