The contents of Baer's work do not require a detailed 

 account. The work is a collection of materials for the 

 future connected with the history of the human embryo. Baer 

 himself wrote in the introduction that his suppositions were 

 to be considered as observations relevant to the study of 

 the history of human fetus, and not as complete descriptions 

 of the later stages of human formation. He noted later that 

 the earlier stages of different human ova so strongly differed 

 from each other that no investigator could be absolutely 

 correct in his observations, but that which was considered 

 normal, and that which was considered a deviation from normal 

 was beginning to be made clear. Therefore, Baer continued, 

 it is very important that one observer has the possibility 

 to compare a large number of ova. He conveyed his satisfac- 

 tion with the fact that he, by investigation, could confirm 

 that aborted ova are frequently abnormal. 



Baer's descriptions of human fetuses follow their ages, 

 which can be judged by data of a preliminary case study and 

 by features of the embryos and their membranes. 



Unquestionable interest is represented by case 1, 

 relating to an extremely early stage. Because early 

 diagnosis of pregnancy is very difficult, Baer considered 

 it necessary to include for this case the following data 

 concerning the duration of pregnancy: "In the summer of 

 1826 in the Anatomical Institute of Konigsberg the corpse 

 of a servant was obtained, found in Pregel. It was learned 

 that the young girl had spent half a day with a young man 

 eight days earlier. She returned home very sad and anxious. 

 Her death by drowning was not accidental but deliberate. 

 Anatomical investigation showed the presence of a recent 

 pregnancy. I supposed, that the determination of the 

 duration could be considered correct" (p. 5). 



On the convexity of one of the ovaries, Baer found a 

 slit-shaped opening of crescent form which was beginning to 

 grow. Cutting the ovary he found there a cavity covered with 

 a yellow mass; from outside the yellow body was covered by a 

 layer of cellular tissue, the outer layer of the capsule of 

 the evacuated Graafian follicle. The uterus was not increased 

 in size, but was somewhat swollen; its anterior wall was 

 farther from the posterior than normal. The internal surface 



443 



