390 GYNECOLOGY 



4. Antagonism between maternal organism and ovum. 



5. Functions of the placenta. 



Determination of Sex. From the time of Hippocrates to the 

 beginning of the eighteenth century, about five hundred theories 

 relative to the question of sex-determination had been advanced. 

 During the last two hundred years this number has been consider- 

 ably increased. At the beginning of the twentieth century, it must 

 be frankly admitted that the problem of sex-determination in the 

 higher vertebrates generally still remains to be solved. The most 

 important observations and experiments bearing on the question 

 have been made during the last fifty years, and from a study of 

 these it would appear that the most exhaustive researches in com- 

 parative and experimental embryology and physiology will be neces- 

 sary before the difficulties of the subject can be elucidated. The 

 data furnished by the study of human beings are scanty and of little 

 value. Most of the statements which have been made are speculative 

 in nature, or of doubtful accuracy. Certain it is also that all attempts 

 to regulate the production of sex in the human fetus in utero have 

 met with failure. 



In many countries the belief has long been current that the sex 

 of the human fetus could be modified during a greater or less period 

 of its uterine life. Now we know that the sex is fixed at least by the 

 beginning of the second month, for at that time the microscope can 

 distinguish ovarian from testicular structure. It is, therefore, 

 scarcely credible that any reversal of sex can be brought about after 

 this period by any conceivable combination of influences. We must, 

 indeed, look to conditions existing during the first month of gesta- 

 tion, or at the time of the meeting of spermatozoon and ovum, or to 

 influences affecting either or both of the latter before conception, in 

 order to find explanation of sex-determination in the human embryo. 

 Those who believe that both sperm and ovum share in the production 

 of sex refer to the various statistics giving the relationship of the 

 parental ages to the sex of the offspring. Hofacker in 1823, and Sadler 

 in 1830, independently stated, as the result of an analysis of about 

 2000 births, that when the father is the older the offspring are 

 preponderatingly male; while if the parents be of the same age, or if 

 the mother be older, there is a larger percentage of female children. 

 This generalization, termed the law of Hofacker and Sadler, has been 

 the subject of much debate, having been upheld by some and denied 

 by others during the last 70 years. 



Those who believe that the influences determining sex belong 

 to the ovum entirely find no evidence to support them from a study 

 of the highest forms of life, though there is strong corroboration 

 from investigations made among lower forms. Thus in cases of 

 parthenogenesis it is evident that the influence of a male paternal 



