16 HUMAN MAGMA KfiTICULfi IN NORMAL AM) I'ATHOI.OCKWL DEVELOPMENT. 



elastic-tifssue stain. I liave also t^howii that the younger the connective-tissue 

 syncytium is, the more difficult it is to digest it in pepsin. Frozen sections shrink 

 but little when treated with acetic acid, while white fibers become transparent. 

 The syncytium itself is somewhat elastic, as shown l)v pressure upon the cover- 

 glass over a frozen section. If treated for 24 hours with pepsin, the lihrils disin- 

 tegrate. The}' are therefore much more resistant to the action of jiepsin than are 

 white fibrils. 



The action of pancreatin is, in a mea.sure, the opposite of that of jiepsin. When 

 the main mass of syncytuim is formed by exoplasm, it digests readily in ])ancrea(in. 

 The more the syncytium is developed, the more resistant it is towards i)ancreatin. 

 Very young sj'ncytium fibrils, therefore, react towards pancreatin and pepsin much 

 like elastic fibers and this is confirmed in a measure, by tinctorial methods, when 

 applied to sections of the chorion and magma, in sjiecimen No. 830. 



I have discussed the denser strands of tissue within the main mass of the 

 magma. In the fresh state it appears that these are distinct fibrils, as shown in 

 plate 3, figure 2. They are, also, observed in plate 1, figure 3. It is not quite so 

 clear that there are fibrils in the magma as shown on plate 1, figure 4. In fact, it 

 apjiears as though we have compartments separated by membranes, and that at 

 the junction of several of these membranes the fibrils become denser, and therefore 

 often appear as distinct fibers. It would be more appropriate than to state that the 

 exoccelum is l>roken up into compartments the walls of which are composed of 

 meml)ranes, and that where several of the membranes come together the increased 

 amount of tissue gives the i)oint of juncture the appearance of fibers to the naked 

 eye and under the enlarging lens. 



I have taken great pains to follow the cells which mark the stronger bands of 

 magma, and it is difficult to arrive at any conclusion, for, in a measure, thej' seem 

 to be related to the endothelial lining of the exoccrlom. In the Peters ovum the 

 spaces near the embryo are lined by a distinct layer of cells, but otherwi,se there is 

 no indication of endothelial lining in any other portion of the chorionic cavity, nor 

 is there any indication of such a lining in the figures given by Herzog, Johnstone, 

 Jvmg. or Strahl and Beneke. It would seem that what corresponds to the exoccelom 

 of the chorion in the later stages is represented by a diffuse mass in the si)ecimen of 

 Bryce and Teacher where the nuclei are scattered through it. The mode of the 

 destruction of the mesenchyme is well indicated in figures on page 18 of a monograi)h 

 by Strahl and Beneke. These irregular cells are first of all attached to the h(\Mvi(M- 

 strands of magma, and they must, therefore, correspond to the endothelial lining 

 of the exoccelom. For the present, however, it appears as if the exoccelom of the 

 human chorion is lined only in part bj' a layer of endothelium; these cells also 

 accompany the magma fibers and line the inner side of the chorion near the emliryo. 



As the amnion exixuids, it naturally pushes theso strands of magma up against 

 the chorion, and in a short time we can recognize only a few fibrils in the exoca'lom 

 which encircle the umbilical cord. These are well seen in specimen Xo. 148, and 

 their remnantsare shown in Xo. 576, of which I give an illustration on i)late 2, figure 2. 

 Xo. 148 is luidoubtedly normal, for it was obtained by mechanical means, and Xo. 

 576 is also a normal s{)ecimen obtained from a tubal pregnancy. 



