Of the White-line, and Peritonaeum or Rim of the Belly.
THe White-line is nothing else, than the bound and extremities of the muscles of the Epi∣gastrium, distinguishing the belly in the midst into two parts, the right and left.* 1.1 It is cal∣led White, both of its own colour, and also for that no fleshy part lyes under it, or is placed above it. It is broader above the Navel, but narrower below, because the right muscles do there grow into one. Now we must treat of the Coat or Membrane, Peritonaeum or Rim of the Belly;* 1.2 it is so called, because it is stretched over all the lower belly, and particularly over all the parts contain∣ed in the ventricle, to which also it freely lends a common coat. It hath a spermatick substance,* 1.3 as all other membranes have; the quantity of it in thickness is very small, (for it is almost as thin as a Spiders web) yet differing in divers places in men and women; for men have it more thick and strong below the navel, that so it may contain the extension of the stomach, often stretched beyond measure with meat and drink. On the contrary, women have it so thick and strong below their navel, that it seems double, that so they may more easily endure the distention of their womb, caused by the child contained in it. But above the navel, men and women have the Peritonaeum of an equal strength, for the self same reason. The longitude and latitude of it is known by the cir∣cumscription of the belly.
The figure is round and somewhat long; it puts forth some productions, like finger-stalls,* 1.4 both for the leading and strengthening the spermatick vessels, and the Cremaster muscles of the Testicles, and, besides it, the ejaculatory vessels; as also to impart a coat to the Testicles, and all the natural parts.
It is composed of slender, membranous and nervous fibers,* 1.5 certain small brauenes of veins and arteries concurring with them, which it receives for life and nourishment from the adherent parts.
This membrane is one in number, and besides every where one and equal, although Galen would have it perforated in that place where the spermatick vessels descend to the Testicles; But,* 1.6 in truth, we must not think that a hole, but rather a production, as we said before.
The later Anatomists have observed, the Coat Peritonaeum is doubled below the Navel, and that by the spaces of these reduplications the umbilical arteries ascend to the Navel.
It is situate near the natural parts, and compasses them about, and joyned by the coat,* 1.7 which it gives them, as also on the sides, it is joined to the vertebra's of the loins, from whose Ligaments (or rather Periosteum) it takes the original: On the lower part, it cleaves to the share-bone, and on the upper to the Midriff, whose lower part it wholly invests; on the fore or outer part it sticks so close to the transverse muscles, that it cannot be pluckt from them but by force, by reason of the complication and adhaesion of the fibers thereof with the fibers of the proper membrane of these muscles; which membrane in Galen's opinion proceeds from this Peritonaeum,* 1.8 so that it is no marvail that we may more easily break than separate these two coats. It is of temperature cold and dry, as all other membranes.
[Use.] It hath many uses, the first whereof is, to invest and cover all the parts of the lower belly, specially the Kall, lest it should be squeezed by great compressures and violent attempts into the empty spaces of the muscles, as it sometimes happens in the wounds of the Epigastrium, unless the lips of the Ulcer be very well united; for then appears a tumor about the wound by the Guts and Kall thrusting without the Peritonaeum into those spaces of the muscles; from whence proceeds cruel pain.
Another use is, to the further casting forth of the excrements by pressing the ventricle and guts on the foreside, as the Midriff doth above, as one should do it by both his hands joyned together.
The third use is, it prohibits the repletion of the parts with flatulency after the expulsion of the excrements, by straitning and pressing them down.
The fourth and last is, that it contains all the parts in their seat, and binds them to the back∣bone, principally that they should not fly out of their places by violent motions, as by leaping, and falling from on high.
Lastly, we must know, that the Rim is of that nature, that it will easily dilate it self, as we see in Dropsies, in women with childe, and in tumors against nature.