THE HUMAN MAGMA llETICULE IN NORMAL AND IN PATHOLOGICAL 



DEVELOPMENT. 



By Franklin P. Mall. 



INTRODUCTION. 



Students of embryology are familiar with the jelly-like substance found in the 

 human exocoelom, which varies much in appearance in different specimens. Some- 

 times this substance is gelatinous, with delicate fibers; at other times it is mixed 

 with granules; and, in extreme cases, it forms quite a solid body. I think it was 

 Giacomini who pointed out definitely that the morphological appearance of the 

 magma determines, with considerable certainty, whether or not the contained 

 embryo is normal or pathological. We are indebted to him for about a dozen papers 

 on pathological embryology, a summary of which he published in Merkel-Bonnet's 

 Ergebnisse. In this summary the following statement is made: 



" In the early stages of development we can determine by the extent of the exocoelom and its 

 contained magma whether or not the embryo under consideration is normal. A large coelom, con- 

 taining a rich magma, with its meshes sufficiently filled with a flaky precipitate to mask the embiyo, 

 is a certain sign of pathological development." 



It is well known that the magma is least conspicuous in fre.sh specimens and 

 becomes more pronounced after being hardened in alcohol or other preservative 

 fluids. In recent years it is found that magma shows to the greatest advantage in 

 specimens hardened in formalin; the fibrils are somewhat tougher, but the magma 

 has usually the same appearance as in the fresh state. However, the experience of 

 embryologists has been that the magma is more pronounced in pathological speci- 

 mens, and for this reason it has been suspected that it does not exist in normal devel- 

 opment. In fact, the illustration of the magma given by Velpeau in his monograph — 

 in which he first uses the term "magma reticule" — is undoubtedly of a pathological 

 specimen. A glance at the other plate which accompanies this handsome mono- 

 graph shows clearly that most of the specimens he describes are decidedly pathologi- 

 cal. During the 80 years which have elapsed since his time, embryologists, through 

 comparative study, have been able to separate normal from pathological embryos 

 with considerable precision; and in the abortion material, as collected in various 

 laboratories, far over one-half of the specimens of the first 2 months of pregnancy 

 are pathological, and in them we usually find a highly differentiated magma. How- 

 ever, if normal specimens are studied with care, we find that they, too, contain some 

 magma; therefore, magma must be viewed as a normal constituent of the human 

 ovum. 



It has been shown by Keibel that there is marked magma within the exocoelom 

 of monkey embryos. In specimens containing embryos 1.3 mm. and 5 mm. in 

 length, he describes it as a flaky, reticular mass outside the amnion, and speaks of it 



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