386 Maximilian Herzog. 



with it, are seen long slender fibers, more or less mixed with 

 granular detritus. These fibers are evidently the remnants of de- 

 generated, dropped-off lining mesoderm cells. The latter themselves 

 are comparatively long and fusiform, with very gradually taper- 

 ing long bipolar processes. Their protoplasm is finely and distinctly 

 granular, well eosin-staining. The nuclei are oval, sometimes al- 

 most rod-like, with rounded ends like the nuclei of involuntary 

 muscle cells. They have a fine but darkly-staining chromatin retic- 

 ulum ; often one or two nucleoli can be seen. The chorion mesoderm 

 in most sections has slightly retracted from the trophoblast ectoderm 

 and we here can see distinctly along the outer margin of the meso- 

 dermal lining a fine, sharply-cut membrana limitans, as described 

 by Bonnet, in a more advanced older ovum as separating the meso- 

 derm of the villi from their ectoderm. The chorion mesoderm forms 

 teat-like or finger-like processes arising from the periphery and 

 extending outwards into the ectodermal trophoblast. These processes 

 likewise show the fine limiting membrane. Sometimes these pro- 

 cesses arise near each other, but they do not yet show any diehotomous 

 division. Here and there are seen fioating in the exocoelom bands 

 or filaments of mesoderm cells. They are interesting from the stand- 

 point of the pathologist, because their occasional growth and per- 

 sistence may lead to the formation of those so-called amniotic bands 

 responsible for disturbance in the normal development of the em- 

 bryo. These mesodermal bands and strands, crossing the chorionic 

 cavity, have also been described for their respective specimens by 

 Bryce and Teacher, Peters and Jung. They are important because 

 they have been interpreted as the remnants of a once solid mass of 

 mesoderm, existing before the formation of the coelom and exo- 

 coelom. 



Keibel (Normentafeln, Vol. 8, p. 12) in discussing the early 

 mesoderm and the formation of the exocoelom says: "In man at 

 a stage when a primitive streak cannot yet be demonstrated with 

 certainty or even does not exist, we find the whole embryonic shield, 

 yolk sac and amnion richly surrounded by mesoblast, as is also the 

 internal surface of the chorion. Spee, in describing his embyro H, 

 says: 'It appears almost inconceivable that the region of the still 



