The placenta, being rapidly formed and being composed of a tissue intended for temporary purposes, is specially liable to various degenerations and to disorders of the circulation.

Haemorrhage occurs in the placenta not infrequently, producing localized collections of blood, the condition being called Apoplexy of the placenta. The placenta villi are embedded in the coagulum and somewhat concealed.

The White infarction is a somewhat frequent lesion in the placenta. It is found in cases where the child has been still-born, and it implies grave disturbance of the circulation in the placenta. The infarction forms a solid white mass, usually wedge-shaped, and generally multiple. In it the villi are dead, and fibrine or blood lies in the spaces. The lesion has arisen by a process of Coagulation-necrosis like the pale embolic infarctions of the kidney and spleen.

The cause of this localized necrosis is not clear. There is probably an arterial obstruction, which Ackermann has ascribed to a periarteritis nodosa. According to Kustner serious nutritive disturbances during pregnancy are regularly followed by the formation of numerous white infarctions of the placenta.

Inflammations of the placenta are described as leading to fibrous thickenings. The inflammation originates in the decidua and extends to the placental tissue.

A Periarteritis nodosa has been mentioned above as having to do with the formation of the white infarctions. It appears indeed that these infarctions are often regarded as due to inflammations. The whole subject is in need of further elucidation.

Syphilis leads in the placenta to new-formation of granulation tissue and gummata, causing the placenta to increase in bulk and weight. From the pressure of the new-formed tissue on the vessels, there is apt to be degeneration of the placental structures. Tuberculosis has also been described as occurring in the human placenta.

Retrograde changes are frequent in the placenta. Fatty degeneration and calcareous infiltration occur in the various structures. The placenta is sometimes speckled all over with small whitish spots, which are areas in which calcareous deposition has occurred. Along with this the microscope reveals fatty degeneration.

Literature

Spiegelberg, Text-book of Midwifery (Syd. Soc. trans.), 1887. Hydatid mole - Virchow, Geschwulste, i., 409; Volkmann, (Destructive mole) Virch. Arch., xli.; Jarotzky and Waldeyer, (do.) ibid., xliv. Placenta - Maier, (Inflammations) Virch. Arch., xlv.; Ackermann, ibid., xcvi.; Kustner, ibid., cvi.; Virchow, (Syphilis) Geschwulste, ii., 480; Fraenkel, Ueber Placentafsyphilis, 1873; Schmobl u. Kockel, (Tuberculosis) Ziegler's Beitriige, 1894, xvi., p. 313.