14 CYCLOPIA IN THE HUMAN EMBRYO. 



esting, as both parents and grandparents were perfectly healthy and monsters were 

 not known to have occurred in the family. The mother had been pregnant eight 

 times, four of the pregnancies ending in abortions. The first child had harelip, 

 the second had cleft palate, the third was normal, and the fourth pregnancy 

 resulted in the cyclopean twins. In my own experience I can report an even more 

 remarkable case. In 1900 a pig uterus was brought to me which contained a 

 number of normal embryos and three cyclopean embryos, all of about the same 

 stage of development. The cyclopean pigs measured about 40 mm. in length, and 

 each of them had a marked depression in the front of the head and a single pig- 

 mented eye with a snout over it. Unfortunately I did not keep the uterus of this 

 specimen, so that it was impossible for us to examine it with care. 



The somewhat lengthy discussion on the differentiation of the eye from the 

 medullary plate is justifiable, because at least one of the specimens I have to 

 report is practically a perfect one, which enables me to discuss the origin of the 

 cyclopean eye in a somewhat connected way, from the condition found in normal 

 embryos. After a description of this specimen I purpose to compare the eyes and 

 brain with the same structures in several younger embryos in the Carnegie collection, 

 as well as with those found in the literature. I shall begin with the smallest speci- 

 men to be described, namely, No. 559. 



EMBRYO, CR 6.5, NORMAL IN FORM, WITH CYCLOPIA, CARNEGIE COLLECTION, No. 559. 



This interesting specimen was sent to me by Dr. Merrill, of Stillwater, Minne- 

 sota, on December 21, 1911. Dr. Merrill writes that the specimen came from a 

 white American, who is the mother of one child, 9 years old. The patient gives 

 a subsequent history of three of four abortions which took place early in preg- 

 nancy. The last menstrual period before the present abortion occurred on 

 October 27, 1911. The abortion followed on December 20. No particulars are 

 obtainable to account for the abortion and there is no evidence of its having been 

 produced by mechanical means. The patient has a history of irregular men- 

 struation and has been treated for metritis and endometritis. It is impossible 

 to obtain any history of venereal disease. 



The unopened ovum, measuring 20 by 15 by 12, came to us fixed in formalin. 

 It is almost entirely covered with villi which branch three of four times and are 

 about 3 mm. long. On one side there is a small area without villi, covered only 

 by the transparent chorionic membrane. Through this can be seen a well-formed 

 embryo, apparently normal, measuring about 8 or 9 mm. in length and filling about 

 one-half of the ovum. The remaining half is filled with dense reticular magma. 

 The umbilical vesicle is spherical, measuring about 3.5 mm. in diameter. The 

 appearance of the ovum before and after opening is shown on plate 2, figures 2 

 and 5. The embryo was removed by cutting the umbilical cord near its attach- 

 ment to the chorion. Photographs were then made at both sides of the embryo, 

 at one diameter enlargement, care being taken to get the exact profile pictured. 

 Numerous other photographs were taken, and it then became apparent that we 

 were dealing with an embryo with a very curious deformity of the head. We 



