HUMAN MAGMA RETICUL!-; IN NORMAL AND PATHOLOGICAL DEVELOPMENT. 17 



The conclusion regarding the condition of the magma of normal development 

 is that the cavity of the ovum is filled with delicate fibrils which are interpersed 

 with numerous nuclei and which form one continuous network, extending from the 

 embryo to the chorionic wall, and blending with its connective-tissue network. It 

 forms one continuous syncytium, and as the ovum grows the magma reticule 

 differentiates somewhat. Stronger bands of membranes soon form, breaking the 

 cavity of the chorion into compartments. This process continues until the amnion 

 begins to expand, and then these fibrils are pushed up against the chorionic wall. 

 The exocoelom begins as two larger spaces near the embryo, and in this portion of 

 the ovum its cavity is lined with a layer of endothelium. It is quite certain that 

 this sharply defined cavity does not extend to include the whole cavity of the ovum, 

 but the cells lining it arise in common with those which accompany the magma 

 fibrils. The exact extent and the fate of the two small spaces near the embryo in 

 the Peters specimen is still undetermined, but Waterston's specimen indicates that 

 they do not extend to fill the entire chorionic cavity. The examination of numerous 

 specimens, however, indicates very definitely that the exoccelom of the ovum at 

 2 months does not contain a complete endothelial lining. 



THE MAGMA IN PATHOLOGICAL OVA. 



Since the publications by Giacomini it has become well known that an increased 

 quantity of magma within the coelom indicates with certainty that the embryo is 

 pathological. When the magma is pictured or described, it is (juite easy to deter- 

 mine whether or not the embryos and ova published in the literature are normal or 

 l)athological. This is demonstrated in the plates accompanying Veljieau's work. 

 His was able to separate most of the normal from the pathological embryos, but he 

 relied mainly upon the external form of the specimens, which he compared with 

 other mammalian embryos. Unless an embryo appeared much like those of other 

 mammals and was not transparent and sharply defined, he decided that it was not 

 norrnal but pathological. The work of Hochstetter, who limited his study to 

 embryos obtained through hysterectomy, has been used to advantage by Keibel and 

 Else in the preparation of their Normentafel, so that now we have adequate tables 

 and jilates which enable us to recognize with considerable certainty whether or not 

 an embryo is normal, ^without paying much attention to the magma or the chorion. 

 However, embryologists are well aware that they can predict whether a specimen is 

 normal or pathological by tlie quantity of the magma which masks the embryo 

 when the ovum is opened. 



By the contents of the exocoelom it is quite easy to classify i)athological ova 

 into three chief groups. In the first group, which includes most pathological 

 specimens, the magma is changed into an organized mass of reticular fibrils, inter- 

 mingled more or less with granular substance. 



To the second group belong si)ecimens in which the exocoelom is large and contains 

 only a fluid mass — that is, a litjuid substance which does not coagulate in either 

 formalin or alcohol. I have pictured a number of specimens of this sort in my 

 paper on monsters. Specimen No. 512, of which I give an illustration on plate 2, 

 figure 1, belongs to tliis grouii. The embryo is atrophic, and it is (juestionabk" 



