| 释义 |
fulcrum|ˈfʌlkrəm, ˈfʊl|
Pl. fulcra. Also 7 fulchrum.
[a. L. fulcrum (in class.L. ‘the post or foot of a couch’), f. root of fulc-īre to support, prop.]
1. a. A prop or support; now only spec. in Mech. the point against which a lever is placed to get purchase or upon which it turns or is supported.
1674Petty Disc. Dupl. Proportion 41 Square Rods..whose Ends let be supported with convenient Blocks or Fulcra. 1690Boyle Med. Hydrostat. ix. 60 The Ballance hangs on a stable Fulcrum. 1774Goldsm. Nat. Hist. (1776) VII. 182 They [serpents] entirely want a fulcrum, if I may so express it, from whence to take their spring. 1802Paley Nat. Theol. viii. §2 The same spine was also..to afford a fulcrum, stay or basis for the insertion of the muscles which are spread over the trunk of the body. 1803J. Wood Princ. Mech. iv. 50 The Lever is an inflexible rod, moveable upon a point which is called the fulcrum or center of motion. 1832H. T. De la Beche Geol. Man. (ed. 2) 40 If the centre of gravity of the mass chances to be high and far removed from the perpendicular of its fulcrum, the stone falls from its elevation. 1855Holden Hum. Osteol. (1878) 141 The use of the scapula is to afford a movable fulcrum for the motions of the arm. 1869Gillmore Reptiles & Birds ii. 59 They hook themselves on to a tree, which gives them the power of a double fulcrum.
b. fig.
1678Cudworth Intell. Syst. 472 The most excellent Fulcrum of the Soul, the perswasion of the Everliving God. a1679T. Goodwin Wks. (1682) II. iv. 335 Our Hearts will need a most special strong fulchrum, support and susteiner (as the word imports). 1804W. Taylor in Ann. Rev. II. 334 This..should have been selected as the fulcrum of indignation. 1850Merivale Rom. Emp. (1865) I. iv. 172 The consulship was the fulcrum from which the whole Roman world was to be moved. 1853Sir H. Douglas Milit. Bridges (ed. 3) 222 A footing once gained is a fulcrum which should never be lost.
2. (Chiefly pl.)
a. Bot. Accessory organs or appendages of a plant; e.g. bracts, stipules, tendrils, etc.
1785Martyn Rousseau's Bot. xxxi. 485 The parts I now allude to, are what he [Linnæus] calls Fulcra, props or supports of the plant. 1807J. E. Smith Phys. Bot. xvii. 218 Of the several kinds of Fulcra, or Appendages to a plant. 1874Cooke Fungi 62 In an exotic genus..the fulcra, or appendages..are black.
b. Ichth. (pl.) The small osseous scales arranged in a row and situated on the anterior ray of the fins of many ganoid fishes.
1880Günther Fishes 360 Vertical fins with a single series of fulcra in front. 1885tr. Claus' Zoöl. II. 164 The spine⁓like splints known as fulcra.
c. Zool. The stem or median part of the incus of the mastax of certain rotifers.
1856[see ramus 3]. 1886C. T. Hudson Rotifera I. 118 The trophi consist mainly of two ribbed rami, attached to a long narrow plate (the fulcrum). 1896Cambr. Nat. Hist. II. 210 In the ventral wall of the gizzard of most Ploima is a median piece, the fulcrum, from which run forwards and upwards two pieces, the rami, which are hinged on the fulcrum. The Y-shaped structure formed of these three pieces is called the incus (anvil). 1951L. H. Hyman Invertebrates III. xiii. 88 The fulcrum, the median, usually posterior piece, is commonly a thin plate lying in the sagittal plane of the body. 1967P. A. Meglitsch Invert. Zool. viii. 261/1 The fulcrum and rami together form the incus.
d. In trilobites (see quot. 1909).
1900C. R. Eastman tr. Zittel's Text-bk. Palaeontol. I. 612 The distal portion [of the pleura], beginning at the fulcrum, may continue of equal thickness. 1909Cambr. Nat. Hist. IV. 234 At some distance from the axis the pleurae are bent downwards and backwards. The point where this bend occurs is called the ‘fulcrum’; it divides the pleura into an internal and an external part. 1953Shrock & Twenhofel Princ. Invert. Paleontol. (ed. 2) xiii. 583 (caption) Fulcrum.
e. Ent. In Diptera, a chitinous portion of the pharynx.
1910C. G. Hewitt House-Flies 12 The Fulcrum.—This chitinous portion of the pharynx..lies on the lower part of the head and in the rostrum. 1925A. D. Imms Gen. Textbk. Ent. 597 Situated within this region is a complex framework of chitin known as the fulcrum, which forms a kind of case enclosing the pharynx, and is present in almost all Diptera. 1951L. S. West Housefly iii. 51 Its [sc. the rostrum's] internal support consists chiefly of a large stirrup-shaped sclerite, the fulcrum. |