338 On the Progress of Embryology in the Year 1840. 



tion of the germinal membrane in one of these two ways. Both 

 theories had been put forth before the discovery of the germinal 

 spot. But when the existence of the latter became known, 

 the discoverer of the same said that probably the macula 

 germinativa represented the first foundation of the germinal 

 membrane. This conjecture obtained more probability from 

 the obvious fact, that the number, size and distribution of the 

 germinal spots alternated according to the different stages. 

 Research, however, first in the Mammalia, and then in Rep- 

 tiles and Fishes, showed that in consequence of fecundation 

 the interior of the germinal vesicle presents new cells, or that 

 (as was seen in the Rabbit) within the germinal vesicle new 

 cells are really built up upon the foundation of the germinal 

 spots." (Introductory Remarks, p. 13.) 



First stages in the development of the fecundated ovum, espe- 

 cially that of the Mammalia. As was already remarked in the 

 introduction, the most important publications of the past year 

 concerning embryology are concentrated in the subjects of 

 this chapter. We will therefore, before presenting some ex- 

 tracts of the details, state the most important results. With 

 few exceptions, to be mentioned, all the observations have re- 

 ference to the Mammalia, and indeed to the Rabbit. 



1. At the period of the rut certain changes have already 

 taken place in the ovarium, the [Graafian] follicles, and the 

 structures appertaining thereto. Through an increased con- 

 gestion of the ovary single follicles become more strongly de- 

 veloped. The germinal spot, which gives the impulse to the 

 formation of the new cells, probably undergoes changes of 

 this kind. From the observations of Negrier, above men- 

 tioned (p. 248), it may be conjectured that in the human fe- 

 male also the period of menstruation is attended by similar 

 phaenomena. 



2. Fecundation itself apparently comes to pass in the following 

 manner: a portion of the semen that has been brought to the 

 surface of the ovarium probably passes into the ovum, and 

 gives the stimulus to the formation of cells within the germinal 

 vesicle******. 



3. The number of ova prepared for fecundation by the rut, 

 does not correspond with the number of the subsequently fecun- 

 dated ova, but generally exceeds the same. This fact, already 

 known, has been confirmed by the latest researches on the 

 Rabbit. 



4. It often happens that more ova pass out of the ovary than 

 are fecundated, or at least than become developed. Herein ac- 

 cord the observations of Barry with those of Pappenheim. 

 The former found in the tubes and uterus unfecundated or 



