Leeuwenhoek in the semen of men, also are considered the 

 base for the formation of the human fetus" (p. 4). 



Turning to the role of woman in reproduction, Hulst, 

 in accordance with current opinions, accepted that the mother 

 "gives the semen a comfortable shelter, warms it and defends 

 it against unsuitable effects" (p. 4). The ovaries were 

 considered the organ of reproduction in women; vesicles formed 

 on their surface. These vesicles (ova) were fertilized by 

 the semen which penetrated into their fluid contents, and 

 they were carried through the fallopian tube to the uterus. 

 Hulst noticed that the changes which the semen caused in 

 the ovum and in the woman's body after conception remained 

 unclear. In any case he considered it established that the 

 internal surface of the uterus, having received the fertilized 

 ovum, became soft because of the outflow of blood from the 

 open ends of the vessels. The ovum sank into this blood- 

 enriched superficial layer, held firmly to it by an outgrowth 

 of rootlets. Near the embryo, over the membrane which covered 

 it (chorion), a plexus of arterial and venous vessels formed, 

 giving origin to the placenta. 



Hulst' s discussions of the embryonic structure were 

 more or less in accordance with the preformists' presentations, 

 although not in the current primitive form of absolute 

 preformation. Hulst confirmed that: 



the body of the extremely delicate embryo , united 

 with the placenta by means of the so-called umbilical 

 cord, represents not an accidental union of parts, 

 but a production of divine art according to high 

 mathematical law. It is composed of two kinds of 

 parts — compact and fluid. The compact parts contain 

 the delicate and weak vessels, which are so small 

 that they are difficult to see even with the aided 

 eye. A transparent fluid flows in them, its movement 

 stimulated by the heat of the mother .... From this 

 originally transparent fluid arises pinkish moisture, 

 which eventually becomes red and acquires the 

 characteristics of true blood which is similar in the 

 yolk. In that moment, when this purple-colored fluid 

 appears , the complicated machine arises . This machine 

 is called the heart, with the auricles, two veins, 

 and two arteries belonging to it. (p. 9) 



26 



