Page:A Treatise on the Membranes in General, and on Different Membranes in Particular.djvu/89

SEROUS MEMBRANES. 85 This rubbing is continual wherever these membranes are found.

How is it that the mechanical authors of the last century, who in the organic economy have attributed so much to physical laws, have not imagined that they should find in this friction one of the causes of the propagation of animal heat?

Why has not this friction been added by them to that of the circulation?

117. The external surface of the serous membranes, almost every where adheres to the neighbouring organs; it is in fact rare to see these membranes insulated on both sides.

The arachnoides at the basis of the cranium, and some other examples, form exceptions. This attachment of the serous membranes to their respective organs, is altogether different from those of the fibrous membranes.

In the latter, the passage of the vessels so unites the two parts, that their organization seems to be in common, and that one being removed, the other almost always dies, as is seen in the periosteum in relation to the bones, etc. On the contrary, every serous membrane is almost foreign to the organ which it surrounds; whose organization is not connected with its own.

118. I shall examine hereafter the proofs of the first assertion relative to the fibrous membranes.

These are the proofs of the second assertion in relation to the serous membranes. 1. We very often see these membranes by turns leaving and again cov-