202 STUDIES ON PATHOLOGIC OVA. 



or anencephaly results. To produce a striking result, as in cyclopia, a small portion 

 of the brain must be affected at the critical time, and I think the work of Stockard 

 has shown clearly that this is before the eye primordia can be seen. Consequently, 

 in order to produce a human monster which is to live until the end of gestation, 

 the effect of the altered environment must be reflected from the chorion to the 

 embryo, so that the tissue to be affected is struck at the critical time in its develop- 

 ment. It is inconceivable that cyclopia should begin in an embryo after the eyes 

 are once started in normal development. Moreover, the same is true regarding 

 hare-lip, for after the upper jaw has once been well formed, the abnormality can 

 not develop. We may extend this statement to include club-foot, spina bifida 

 occulta, and other types of malformation. In fact, in discussing the origin of mero- 

 somatous monsters, hardly more has been stated by most authors than that there 

 has been an arrest of development, but I have attempted to point out that the 

 primary cause is in the environment of the egg and that the arrested development 

 is associated with destruction of tissue. 



DESCRIPTION OF PLATE. 



PLATE 7. 



FIG. 83. Normal embryo with cyclopia ; in front of the eye is seen the Cyclopean snout. No. 559. X3.75. 



FIG. 84. Normal double monster. No. 249. X0.75. 



FIG. 85. Specimen with hare-lip and exencephaly. No. 364. X2.25. 



FIG. 86. Specimen with hare-lip. No. 982. XI. 5. 



FIG. 87. Stunted fetus with large hernia in umbilical cord. No. 1330. X0.9. 



FIG. 88. Normal embryo with exencephaly and spina bifida (the latter opposite the arrow). No. 1315. XI. 5. 



FIG. 89. Normal fetus with hernia of mid-brain. No. 1690. X6.75. 



FIG. 90. Anomaly of left hand of No. 306a. Only the thumb and little finger are normal. 



FIG. 91. Left hand, which is club-shaped, from No. 230, a fetus compressus 57 mm. CR. X0.75. 



FIG. 92. Deformed wrist with atrophic radius in a normal embryo. No. 789, 50 mm. CR. X3. 



FIG. 93. Right hand with six fingers from macerated specimen. No. 1749. There were six digits on each of the 



four extremities. X3. 



FIG. 94. Hydatiform villi. (After Gierse.) See Chapter VIII. 



FIG. 95. Hydatiform villi showing vacuolation. (After Gierse.) See Chapter VIII. 



