n.)0 



GENEBAL ORNITHOLOGY. 



which gets hohl of the ovnm to drnp it dnwii to tlie coiinnon lot of inortals from its high ovarian 

 birth. The iufundibuluin receives from the mesentery a delicate tuuic of imstriped muscular 

 fibres, which are so disjiosed as to dilate that orifice for the reception of the ovum ; and duriug 

 the venereal orgasm the mouth of the tube is supposed to seize ujion the ripest egg. Tlii' 

 actual anatomy of the arrangement, and the whole operation, is strangely suggestive of one of 

 the oldest myths respecting tlie serpent whicli bore the egg of the world in its jaws. The 

 mucous lining of the oviduct consists of a layer of ciliat<'d cpitliehum ; the membrane has a 

 different character in successive portions of its extent. Alxive, when the tube is not distended 

 witli its burthen, the lining is thrown into length^-ise folds, wliich lower down l)ecome spirally 

 disposed, and then longitudinal again before they cease. This rugous portion of the tube is 

 beset with mucous follicles, which secrete "the white." The oviduct, after contracting at a 

 point called the isthmus, enlarges to a calibre sufficient to accommodate the egg in its shell; 

 for this is the shell-forming p.-irt, Iiomologous with the manunalian uterus (a sinister semi-uterus 

 at least), lined with large villi, and beset "with the folhcles whose secretions calcify the egg-shell, 

 and decorate it with pigment. The rest of the tube is vaginal, being merely the passage-way 

 by which the perfected ovum is discharged into the cloaca, to be expelled per anmn. The 

 muscular walls of the oviduct consist of both circular and longitudinal unstriped fibres, like 

 those of intestine, — the latter especially in upjier portions and at the infundibulum, the former 

 more cons]>icn(]Usly below, where they form a sort of os tiiica at the bottom of the calcific 

 ]iortion, and a kind of sphincter vayincB at the end of the tube. A recognizable clitoris is 



developed in many birds. 



The deposition of the white and of the shell 

 remains to be noticed. The first deposit upon 

 the yell;-ball i-ousists of a layer of dense anil 

 somewhat tenacious albumen, called the chcda- 

 ziferovs membrane (Gr. xa-^a^a, chalaza, a tu- 

 bercle, and Lat. fero, I bear). As the egg is 

 urged along by the peristaltic action of the 

 tube, it acquires a rotation about the axis of the 

 tube ; the successive layers of soft albunjen it 

 receives are deposited somewhat spirally ; and 

 the chalazifenius membrane is drawn out into 

 Fig. 110. — I-lfn's egcr, ii.'it. sixc, ill pecfimi; from threads at op])osite pides of the egg. These 

 Owen after A. Thouipson. A, cic.tricae or " treiid," threads, fl'hich become twistcd in opposite direc- 

 with Its nucleus, of wlute germ-yelk, floiiting on surface . ' . >. i^^^v, lu , l>[;toii,c uiii.i 



of pale tliin nutritive yell;, leading to ccntr,-il yelk- tions during the rotation of the PSg, are called 

 cavity, r; a, tlie yellow yelk-ball, deposited in tlie sue- chalasa : tliey are the "strings,"' rather uu- 

 cessive layers, fornung a set of /ia/mie.s, .and enveloped .' . ^'' 



in tlie clialaziferous membrane which is spun out at pleasantly evident in a Soft boiled egg, but serve 

 opposite poles into tlie twisted strings, chalazje, <;,c; the important office of mooring and steadyinsj the 

 0, 0', successive investments of softer white albumen; n ■ i . . J '^ - 



il, inembrana putaminis, the " soft shell " or egg-pod, y"'''^ 1" """' s<-'<^ '"'f ^vllite by adhesions eventually 

 lietwcen layers of whicb at the great end of the egg is eontractcd with the membrane which innnedi- 

 t he air space,/; c, the shell. , t i. i , ,, r^ 



ately hues the shell. They are also intrusted 



with the duty of ballasting, or keeping the yell; right side up. For there is a "right side" 

 to the yelk-ball, being that on which floats the cicatricle, or "tread." This side is also the 

 Hghtest, the white yelk being less dense than the yellow; and the chalazfe are attached a little 

 below the central axis. The result is, that if a fresh egg be slowly rotated on its long axis, 

 the tread will rise by turning of the yelk-ball in tlie opposite direction, till, held by the twistins 

 of the chalazse, it can go no farther ; when, the rotation being continued, the tread is carried 

 under and up again on the other side, resuming its superior position as before. After all the 

 spiral layers of soft white are laid on, a final covering of dense albumen is deposited at the 

 isthmic part of the oviduct. This forms a tough tunic called the membrana putaminis (Lat. 



