What is "jacob's membrane"

Membrane \Mem"brane\, n. [F., fr. L. membrana the skin that covers the separate members of the body, fr. L. membrum. See Member.] (Anat.) A thin layer or fold of tissue, usually supported by a fibrous network, serving to cover or line some part or organ, and often secreting or absorbing certain fluids.

Note: The term is also often applied to the thin, expanded parts, of various texture, both in animals and vegetables.

Adventitious membrane, a membrane connecting parts not usually connected, or of a different texture from the ordinary connection; as, the membrane of a cicatrix.

Jacob's membrane. See under Retina.

Mucous membranes (Anat.), the membranes lining passages and cavities which communicate with the exterior, as well as ducts and receptacles of secretion, and habitually secreting mucus.

Schneiderian membrane. (Anat.) See Schneiderian.

Serous membranes (Anat.), the membranes, like the peritoneum and pleura, which line, or lie in, cavities having no obvious outlet, and secrete a serous fluid.

Jacob \Ja"cob\, n. [Cf. F. Jacob. See 2d Jack.] A Hebrew patriarch (son of Isaac, and ancestor of the Jews), who in a vision saw a ladder reaching up to heaven (--Gen. xxviii. 12); -- also called Israel. And Jacob said . . . with my staff I passed over this Jordan, and now I am become two bands. --Gen. xxxii. 9, 10. Thy name shall be called no more Jacob, but Israel. --Gen. xxxii. 28. Jacob's ladder.

1. (Bot.) A perennial herb of the genus Polemonium ( Polemonium c[oe]ruleum), having corymbs of drooping flowers, usually blue. Gray.

2. (Naut.) A rope ladder, with wooden steps, for going aloft.
   --R. H. Dana, Jr.

3. (Naut.) A succession of short cracks in a defective spar. Jacob's membrane. See Retina. Jacob's staff.

   1. A name given to many forms of staff or weapon, especially in the Middle Ages; a pilgrim's staff. [Obs.]
      --Spenser.

   2. (Surveying) See under Staff.