56 ON THE FATE OF THE HUMAN EMBRYO IN TUBAL PREGNANCY. 



the tube, first growing around them and then into them, but there is no response in 

 the tube similar to that which takes place in the uterus. In the tube practically no 

 decidua is formed, and as it seems that the decidua is an important factor in pre- 

 venting extensive hemorrhage, it follows that from the beginning the implanted 

 ovum in the tube must be surrounded by an excess of blood. The blood which is 

 in immediate apposition with the trophoblast does not coagulate and is taken up by 

 the syncytium, which is usually very markedly vacuolated and serves as pabulum 

 for the ovum. All stages of the destruction of the blood corpuscles can be seen in 

 suitable specimens. Particles of red cells are found within the cells of the tropho- 

 blast, where they still take on their characteristic stain. Soon these particles 

 become so small that they blend with the protoplasm of the syncytium, giving to it 

 the tone of the staining property of the red cells, so we can find all gradations and 

 colors from red cells to the well-stained syncytium without demarking sharply the 

 blood pabulum in its digestion by the trophoblast. If the hemorrhage is excessive 

 the blood forms a clot that is, the antibody produced by the trophoblast to prevent 

 coagulation of blood acts only in its immediate vicinity and does not penetrate the 

 larger mass of blood. This clot then becomes a foreign body and can not serve 

 further as pabulum for the ovum. As rapidly as the trophoblast punctures the 

 venous sinuses of the tube it throws up a wall, so to speak, which prevents excessive 

 hemorrhage into the intervillous spaces. If the blood dribbles in slowly, it seems 

 to serve best as pabulum for the ovum. Extensive hemorrhages are prevented by the 

 cells of the trophoblast, which soon change into vacuolated syncytium and thus seem 

 to protect the intervillous spaces. The larger meshes in the syncytium take up 

 groups of red corpuscles, which are held until they fragment and are taken up by 

 the protoplasm in the process of digestion. 



The trophoblast also has a marked tendency to produce a peculiar necrosis of 

 the maternal tissues with which it comes in contact, producing the so-called fibri- 

 noid substance. Apparently this is formed primarily in the mesodermal tissue of 

 the mother, but the fibrin of the blood, the epithelial cells, and the free trophoblast 

 do not seem to escape in this form of necrosis. With the aid of the fibrinoid sub- 

 stance a strong wall is formed between the tips of the villi and the tissue of the tube. 

 This mass then forms a line of demarcation between the ovum and the tube wall, 

 even if the latter be ruptured. The implantation cavity then is lined with much 

 fibrinoid tissue upon which are scattered cells of the trophoblast. Later these indi- 

 vidual cells penetrate the fibrinoid substance, giving it in older specimens the peculiar 

 appearance of cartilage. Tips of the villi penetrate this wall and from them streams 

 of active trophoblast reach out and puncture fresh sinuses. In every respect the 

 condition found in normal implantation in the tube seems to be identical with that 

 found in the uterus, except that there is no formation of decidua. As the decidua 

 may be viewed mainly as an agent to prevent excessive hemorrhage, it can be spared 

 in the tube in case the trophoblast and fibrinoid substance take its place. In fact, 

 in the latter part of pregnancy in the uterus, the decidua does not seem to play 

 any great role. 



All together 43 normal embryos in this collection were obtained from tubal 

 pregnancies. The youngest specimen contains an embryo 4 mm. long, and the 



