of the uterus was rough. Under a microscope, villi and ends 

 of blood vessels were distinguished with the ends of the 

 blood vessels situated not in the villi but between them; 

 the vessels formed a network, submerging in the coagulated 

 nearly transparent mass, which filled the spaces between 

 the villi. Baer considered this condition to be the 

 beginning of formation of the caducous membrane. How the 

 ovum of mammals and man looks, Baer did not know. "If I 

 knew," he wrote, "that these ova represent opaque small 

 bodies, then I may have found also the ovum, although as far 

 as I searched in the oviduct and in the uterine wall for a 

 vesicle with villi or without them, all efforts were useless" 

 Cp. 8). 



Case 2 related to pregnancy which ended due to the 

 mother being scared or frightened in the fourteenth day. 

 The embryonic vesicle was not more than three inches in 

 diameter and covered by delicate villi. From outside, the 

 embryo was not observable. "During the dissection of the 

 ovum," Baer wrote, "I found two slipped combined vesicles: 

 the internal one was smaller than the outer. The rudiment 

 of the embryo was found between them, having the form of 

 an open boat, the length of about 2/3 inch" (p. 9). From 

 the general form of the embryo, it was seen that the back 

 was already formed, and the ventral side was still opened 

 wide. Near the embryo, a cudgel-shaped vesicle, was the 

 allantoic sac. Baer could not find the umbilical vesicle 

 and considered the yolk sac or umbilical vesicle to be the 

 internal vesicle of the embryonic ovum, although it was not 

 clear for him whether it was united with the embryo or not. 



Case 3 presented a three-week-old embryo studied by Baer 

 in detail. He described the general view of the embryonic 

 ovum, the chorion, its villi, the connection of the embryo 

 with other parts of the embryonic vesicle (Figure 33, 5), 

 the amnion, umbilical vesicle and allantoic sac (Figure 33, 

 9) . The embryo and its situation, form and structure are 

 seen in Figure 33, 11. The back of the embryo is closed 

 in all its extension; the occipital protuberance is clear 

 but not strongly protruding. The vesicle of the fourth 

 hillock protrudes significantly and is nearly transparent, 

 since the top of the skull remains very thin there. The 

 lateral fissure is clearly seen, dividing the dorsal and 

 ventral plates. Two convexities are present on the ventral 



444 



