94 CARNEGIE INSTITUTION OF WASHINGTON. 



remained entirely unstained, whereas the cells of the liver, spleen, 

 bone-marrow, and lungs were laden with the phagocytosed particles. 



In another series of experiments Dr. Wislocki introduced solutions 

 of different degrees of diffusibility into the peritoneal cavity of fetal 

 cats and guinea-pigs. When phenolsulphonephthalein, an easily 

 diffusible true solution, is so injected, it is absorbed by the fetal blood- 

 stream and conveyed to the placenta, through which it slowly diffuses 

 into the maternal circulation and is excreted by the maternal kidneys. 

 It is also excreted by the fetal kidneys, being found in the fetal bladder 

 in every instance in which sufficient urine could be collected to test 

 for its presence. When trypan blue, a less diffusible colloidal dye, is 

 injected into the fetal peritoneal cavity, it is absorbed, vitally stains 

 the fetus, and is excreted by the fetal kidneys. It is not, however, 

 transmitted through the placenta to the maternal tissues. 



Mitochondria in the Placenta. 



Inasmuch as the character and distribution of the mitochondria 

 are thought by some to be an index of the metabolic activity of a cell, 

 it is of interest to know the relative distribution of these structures 

 in the maternal and fetal parts of the placenta. With this in mind, 

 a survey has been made by Dr. Wislocki and Dr. J. A. Key of mature 

 placentae from a variety of mammals which were appropriately pre- 

 pared for the demonstration of mitochondria. It was found that, 

 while mitochondria are present in all of the fetal and maternal tissues 

 of the placenta, they are particularly abundant in the cells of the 

 epithelial membrane constituting the barrier between the two circu- 

 lations. They are also abundant in the endothelium lining the 

 maternal blood-channels and in the glands of the uterine mucosa. 

 The functional activity of a given type of cell apparently is the deter- 

 minative factor in the distribution of the mitochondria, rather than 

 any inherent difference between the fetal and adult state. The 

 placentae studied included: (1) the pig, in which the chorion is merely 

 apposed to the folds of the uterine mucosa; (2) the cat, in which a more 

 intimate union results from the invasion of the mucosa by the chorion ; 

 (3) the guinea-pig, in which a still more intimate fusion of the chorion 

 with the uterine wall occurs, including erosion of the maternal vessels 

 and the disappearance of their endothelium, leaving a single layer of 

 chorionic epithelium between the two blood-streams; and (4) the 

 human, in which the conditions are much like those of the guinea-pig. 

 In their final paper, these investigators have carefully described and 

 illustrated the finer histology of these different types and the associated 

 modifications in the distribution of mitochondria. 



PATHOLOGY OF THE FETUS. 



Several papers, based wholly or in part upon the pathological speci- 

 mens and records in our collection, have appeared during the year. 



