Embryonic Development in Man. 383 



where shows profound degenerative changes, and the large cystic 

 glands are partly or completely filled with blood and detritus, as 

 already mentioned. There is no trace of glandular or surface epithe- 

 lium left at the site where the canal takes its origin from the 

 surface. Nor can one find any gland ducts opening into the canal, 

 or into the cavity in which the ovum now is situated. All of the condi- 

 tions point unmistakably to the fact that our own ovum, like that 

 of Peters, penetrated into the decidua not through a gland space, 

 but by eating its way through interglandular tissue of the compacta. 

 It does not appear necessary to us to assume that the ovum can make 

 its way into the decidua only through a spot denuded of the surface 

 epithelium. Since the enlarged gland spaces, even where not in 

 direct contact with the trophoblast, exhibit most marked degener- 

 ation of the lining epithelium, we may well assume that the tro- 

 phoblast, in contact with the surface epithelium, can destroy it 

 easily and make its way into the connective tissue of the decidua. 



In our preliminary communication^ read in August, 1907, before 

 the Zoological Congress of Boston, we said: ''We cannot conclude 

 this preliminary report without pointing out what we might call 

 the pathologic aspect of the early stages of placentation in man. 

 The proliferation of the trophoblast, the manner in which it invades 

 the maternal organism, pushing aside, destroying and changing ma- 

 ternal tissue elements, vascular and other structures, is the exact 

 picture of malignant tumor proliferation, while the reaction of the 

 maternal tissue, taken for itself alone, reminds one forcibly of a 

 profound destructive hemorrhagic inflammation. It is very striking 

 to the pathologist to behold in early placentation, in the apparatus 

 and the phenomena which enable the young ovum to anchor and 

 implant itself firmly into the maternal organism, the very para- 

 digma of two such important pathologic processes as malignant tumor 

 growth and hemorrhagic inflamation." 



A further study of the sections has only strengthened the im- 

 pression gained previously. The destructive tendencies of the early 

 trophoblast of the ovum are certainly very marked. If some hypo- 

 thetical speculations may be here permitted, we would like to ex- 

 press our opinion that the trophoblast at ascertain stage of its 



