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241 The control group (Table 99 ) show no neural defects; an oval rhomboid sinus corresponds to ínciplent histologìcal closure. ln exper¡mental embryos without neural defects (Table 40 ) there are again no cord defects, but in two cases (l8E 44, 30E 4) a closed rhomboid sinus ln serial sectlons was recorded as open in the whole embryos. Embryo l8E 10 should probably be regarded as an example of early myeloschisis, 0f the embryos wÌth histologîcal myeloschisis (Table At ) two were recorded with irregular, rather than regular, defects în the whole embryos (30E 56,42E 8). At the rhomboid sinus one embryo (lBE 59) exhibited an oval rhomboid sinus and elevated neural folds caudal to the lesion, and another (3OE 25) showed a triangular rhomboid s¡nus and closed neural folds. Apart from these four exceptions there is close âgreement between the histological findings and the camera lucida drawings, with a trîangular rhomboid sinus corresponding to early myeloschisis at Stages lJ-14, and a regular cord defect correspondíng to establ ished myeloschisis at Stages 16-20. l'lyelodysplasîa (taUle 4Z ) is characterized by an irregular cord defect wìth only one exception (\ZE 69). At the rhomboid sinus, apparent closure in the whole embryos corresponds to a closed neura¡ tube or to ectoderm covering the defects in the serial sectîons. This comparîson of the appearances of the neural tube and ifromUoia slnus before and after seriaì sectioning reveals that: (") an oval rhomboid sinus is followed by a normal neural closure (b) a triangular rhombold sinus precedes an open neural defect (myeloschisis) (c) a regular neural defect corresponds to hístological myeloschisis
242 (d) an lrregular neural defect represents histologìcal myelodysplasia. As no embryos earlìer than Stage 16 show nyelodysplasìa no comment can be made on the appearance of the rhombold sînus. Thts is consistent, however, wlth the suggestÌon that myelodysplasîa does not ar¡se by abnormal closure of the neural folds, but Lnvolves an absence of neurai plate material and development of the dysplastic cord from tê¡ l-bud material alone after Stage 15.
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E}4BRYOGENES IS OF EXPERIHENTALLY I
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MY PARENTS c.J.H. G. M.
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lt Congenital malformêtlons of the
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TABLE OF CONTENTS SECT ION PAGE 1 I
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},I.ATE R I ALS 3.1 THE CHICK EI4BR
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vt I I 6.3.2 Stage 10 Experímentel
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9 APPENDTCES 378 APPENDIX A . 379 1
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1.1 TERATOLOGY Birth defects have a
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4 of the complexity of normal devel
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6 flat, exposed plaque of neural ti
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8 However, several early embryos in
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.1- 5
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l2 2.1 ErI0L0rL!! fïE qYs34t!1!!jr
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4 which has rema¡ned fairly consta
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6 and about 112 after two (Laure,nc
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l8 ln some very early human embryos
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2l and kinky-ta¡l as disorders of
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23 Vogel and McClenahan (1952) tnus
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I'IATE R IALS 25
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27 lf necessary, eggs were stored a
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FÍg. 5. lncubator allowing precise
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3l 4. r sELEcr I oN !F EGGq 4.1,1 .
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uler. Accurate Staging (Hamburger a
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.\lz '?. t
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Fis. I AsB, Windowìng followed by
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Fis. 9 Aã8. t/indow?ng followed by
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42 ( \--l /) ^ ) t0
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44 serîal sectlonlng a camera luci
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46 Thus the embryos selected for se
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48 TABLE 3. srAGE t0 El,tBRyos (cno
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50 TABLE 5 , Reg i ons srAGE 13:16'
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52 4.8.4 HistologÌcal_De:plþtÍon
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5 RESULTS OF TERAÎOLOGICAL PROCEDU
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(c) deaths and defects in the survi
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Fi g. Percentagcs of early deaths a
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6o MoRTALtTY, AFTER ì,'tNpowtNq,AT
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TABLE B.'DEVEIOPI{ENT'AFTER'WINDOIi
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TABLE 9. ¡4ALFORMATIONS PRODUCED'B
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N=231 ffil e ooyi ffi s oays [il t2
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6B TABLEt loj lloRTALtTy AFTER VtBR
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70 5,3.2 Pa-rôf i Idì ¿irid PIè
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TABLE 13; MALFORI4ATIONS AFTER PLAS
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41 13 0 23 No l^l i ndow Control s
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Fíg. Percentages of early deaths a
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78 ALBUMEN INTRODUCTION Analysís o
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0 1 0 0 a o TABLE 17. I'lALF0RÌ1AT
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N Eorly Deothi N=10ó N a ú, o d,
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103 51 52 28 14 4 6 No W î ndow Co
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Fi g. 14. Percentages of early deat
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88 AtR qELL, REEXPANSI0N Analysls o
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90 5.4 BACTERt4L CUTTURE 0F UlNpohr
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92 TABLE 22. ¡¡UI'ISELTS OF PLATE
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94 6.1 EMBRY0ûIIES I s 0L 0!!\- NE
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Fis. I5 A¿8, Range of s izes (mm.)
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Figs. 16 AaB.. Range of sizes (mm.
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100 6.1.2 f4ortal í!y with Vsrying
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421.. 26 25 I (3.85) 20 (76 .92) 1
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00 N Eorly Deoths ,n -¡ F- ô- xu.
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ì06 Degrees of Freedom 12 Chi Squa
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hzE 53 42C z5 51(96.4)2\(96) 2(3.77
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ffil Op"n Anterior Neuropore I I0 N
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N=380 El Ovol Rhonnboid 'Sinus ì l
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Øl Open Broin Defecls N=384 ffi F"
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ligr. 21 - 30. Camera lucida drawin
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Fi s. 22. lrregular open anteríor
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lmm OPEN BRAIN DEFECT Á,NOPHTHALMI
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lmm OVAL RHOMBOID S¡NUS 48 HOURS S
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FiS. 26, Open neural folds extendin
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t-l lmm IATER OPEN CORD DEFECT . RE
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l2B t--l lmm EARLY OPEN CORD DEFECT
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Fis. 30. Large caudal cyst Ìn an o
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132 6.1 .4 DeveloÞñent of oÞen N
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Fig. 31 . Percentêges of experinen
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36 TABLE ?8. RH0I4B0lD stNUs ctôs
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N=38o H ovol Rhomboid sinus l^ r38
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F¡ S. 33. Percentages Õf open cor
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142 6.1.5 Distríbution of 0pen Cor
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Fi s. "l! Percentage distrìbution
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lrregul ar (Z) somi te be low level
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ì48 N=2ó4 ffi m Regulor Cord Defe
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Fis. 36. Percentage distrîbution o
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152 6.2 sPtIA! LFVELS 0F oPEN CORp
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Fìgs. 37'38, Vertebral defecrs in
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CERVICAT THORACIC LUMBAR FUSED CAUD
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---l r r'I * 40
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t59 a) spîna bif¡da occulta is se
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:al . '**Ç- 4 ff, À(,) ftø 9-' o
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162 lmnediately after closure, sepa
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164 Hensenrs node and the primitive
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-l :: l 48 I 49 i :. t: .lì 50 ì:
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t67 somite area (through asymmetry
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t69 ln both embryos the volume of n
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171 The rhomblc roof became membran
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173 At areas of myeloschisîs conta
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175 neurêl tîssue wíth mesoderm
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t77 e) encroachment of somitîc mes
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ôt rf) , ,,. ì _ ^iiir¡:ù\. I r
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l 55 56 57 58 59 ó0
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Fiss. 65 Early myeloschisis in a St
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fiSr. 71 - 76. Later myeloschisis i
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Fiss. 77 -82. Early myelodysplesia
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FÌgs. B3 - BB. Later myelodysplas
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Figs, 89 - 91. Processíng artifact
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ì86 6.3.10 SequenJ¡¿il ll lúSti
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Fígs. 95 - 102, Sequentiêl drawin
Page 216 and 217: l9o EVERsToN: srAGE rf (o r o+) o @
Page 218 and 219: @ @@ "@ @ e q q a a 192 CoNTROL: ST
Page 220 and 221: MYELOSCHTSTS: STAGE tZ (tZeïl OOG
Page 222 and 223: coNTRO[: STAGE tó (ro c zz) . a@ Q
Page 224 and 225: G (õ--==: \z-- HEMTMYELIA: STAGE t
Page 226 and 227: Som i te Defects contact none sePa
Page 228 and 229: Somite Som i te Contact Defects N'
Page 230 and 231: Som i te Contact Som i te Defects c
Page 232 and 233: none none N) o o\ B r8c 23 12 good
Page 234 and 235: separat ion none contact/ none sepa
Page 236 and 237: Regíon Embryo Stage Conditîon Neu
Page 238 and 239: none none none none none none l'.J
Page 240 and 241: 18E 10 13- vëry poor closed 0 cove
Page 242 and 243: separãtion none contact none conta
Page 244 and 245: Regíon Embryo Stage Condition Neur
Page 246 and 247: separation none sepâ ra t îon non
Page 248 and 249: separâtion none sepa ra t ion sepa
Page 250 and 251: Reglon Embryo Stagd cond¡t¡on Neu
Page 252 and 253: none none none none N) NJ .{ A A A
Page 254 and 255: contact/ none separatlon contact no
Page 256 and 257: Region Embryo Stage Conditlon Neura
Page 258 and 259: TABLE 38D. STAOE 17.20 CONTROL AND
Page 260 and 261: Reglon Embryo Stage Condition Neura
Page 262 and 263: 428 72 20 closed covered none conta
Page 264 and 265: 239 neural tissue ât the later sta
Page 268 and 269: TABLE 39. APPEARANCE OF I,'HOLE EI4
Page 270 and 271: TABLE 40. APPEARANCE OF }/HOLE EI"I
Page 272 and 273: closed closed c I osed c I osed c I
Page 274 and 275: 249 6.6 pEVEL0PMENT 0F rH!_¡Ho|4gl
Page 276 and 277: Emb ryo Stage Rhombîc Roóf Neural
Page 278 and 279: CDE D'E DE CDE DE DE DE D BCD BC BC
Page 280 and 281: TABLE q6,. STAGE 17-20 CoNTRoI AND
Page 282 and 283: Figs- 10J - i11. Development of the
Page 284 and 285: Fî s. tub. Thick rhombic roof in 5
Page 286 and 287: Fig. 109 Hernbranous rhombic roof w
Page 288 and 289: 260 6.7 HrqroLoctcAL, cHANgË Assoc
Page 290 and 291: TABLE 47. CONTROL EMBRYoS.HISTOLOGI
Page 292 and 293: 0 0 0 0 0 0 0 0 0 0 o 0 0 0 0 0 0 N
Page 294 and 295: 42c 21 zo B c D E 0000 00 00 00 1\.
Page 296 and 297: l\t q\ 1oE 26 16 30E 59 16 3oE 77 1
Page 298 and 299: 0 0 0 0 0 0 0 0 0 0 0 0 N) .{ Embry
Page 300 and 301: l\) \l N D E 00 00 0 0 13.79 0 100
Page 302 and 303: N) \¡ \2E 72 20 E B c D' E 00 0 15
Page 304 and 305: 46. 15 76.92 0 20.51 14.83 2i,92 53
Page 306 and 307: ECTODERM DISCONTINUITY IN EXPERIMEN
Page 308 and 309: 279 ECTODERM DISCONTINUITY IN EXPER
Page 310 and 311: SOMITE SEPARATION IN EXPERIMENTAL E
Page 312 and 313: 283 NOTOCHORD SEPARATION IN EXPERIM
Page 314 and 315: 285 SOMITE DEFECTS IN EXPERIMENTAL
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287 and distr¡bfrtíon in the cont
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19.09 r8.95 r 1.84 14.82 15.20 0 17
Page 320 and 321:
0 15. 89 81 .08 100 100 ' 76.92 0 1
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43. rB 100 100 0 12.53 74.07 r00 't
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7.t6 16.03 100 100 160 7.90 18.22 r
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Figs. 120'123. Percentage ie.ngths
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299 O\TERLAP ZONE IN EXPERIMENTAL E
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301 OVERLAP ZONE IN EXPERIMENTAL EM
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303 ând every tenth sectlon was ne
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30c 12 16 c 17707,61 2463.3\ 7.19 D
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Ratio NT/N 4 .90 4.11 6.17 7.14 6.9
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Rêtlo NT/N 4.go \.36 3 .44 3. 18 3
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6.7t 6.lt 4.63 4.60 4.13 3.48 hzE 5
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Fi9s, 124-127, Neurál tube-norocho
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315 NEURAL TUBE -NOTOCHORD RATIOS I
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317 NEURAL TUBE-NOTOCHORD RATIOS IN
Page 348 and 349:
319 TABLE 598 ' ANALYSIS OF VARIANC
Page 350 and 351:
321 TABLE 61., .NEURAL TISSUE/NOTOC
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323 Apart f.rom the sîgnîficant d
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t25 7. Dlscusst0N 1'/i th progressi
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327 C¡osure of the anterior neurop
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329 the mid-polnts of the defects w
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331 'c¡osure of the neural folds w
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333 . These findings s.ugges r that
Page 364 and 365:
335 Lendon (1968, 1975) and notos (
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337 Ferm, 1965; l"larin-Padi r ¡a,
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339 Kôplan (1965) and Kaplan and G
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341 reach the floor-plate; asymmetr
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343 took up the label, shovri.ng th
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345 The defects in early human embr
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347 after pred¡cted closure (Lemî
Page 378 and 379:
349 hours could provide evidence fo
Page 380 and 381:
351 t971), Gal lus and Xenopus (l'l
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353 1962i 1965). Barth and Barth.(1
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The result of any teratogen¡c insu
Page 386 and 387:
357 Uindowîlg at ear¡y stages of
Page 388 and 389:
SUHHARY AND CONCLUS I ONS
Page 390 and 391:
361 separatlon between the neural p
Page 392 and 393:
363 APPENDIX A Preparatlon of Early
Page 394 and 395:
365 APPENDIX B Stainl.ng of Carti l
Page 396 and 397:
367 10, BIBLIOGRAPHY, Alter, l.,l.
Page 398 and 399:
369 Braun, l'{. (1882). entwicklung
Page 400 and 401:
371 Crlley, B,B.(1969). Analysîs o
Page 402 and 403:
373 dqs anomal ies de lrorganizatio
Page 404 and 405:
375 Heath, H.D., Shear, H.H., lm€
Page 406 and 407:
377 Jel inek, R. (1960). Developmen
Page 408 and 409:
379 Laurence, K.14. (1964). Thé na
Page 410 and 411:
381 McKeown, T. and Record, R.G.(19
Page 412 and 413:
Penrose, L. S.(1957). Genetics of a
Page 414 and 415:
385 Russell, H.E. and A¡ tken' G.T
Page 416 and 417:
387 Spemann, H. (1938). Embryonic D
Page 418 and 419:
389 lJeed, ¡.H. (1937 -38'). M.nin
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