238 DR. E. KLEIN. 



* Anatomy of the Lymphatic System ' (part i, serous 

 membranes) I stated that under pathological conditions 

 bud-like and papillary or villous projections grow out from 

 the surface of the serous membranes (tenestrated as well as 

 non- fenestrated parts), and that the connective tissue forming 

 the matrix of the larger or further advanced papillae does 

 not seem to be produced by the distinct conversion of the 

 substance of endothelial cells, as stated by Kundrat (' Strie- 

 ker's Jahrbiicher,' 1870), but appears rather as a kind of 

 secretion. This, however, is certainly not correct in the case 

 of the projections of the normal omentum as described above, 

 for here the newly formed connective-tissue bundles are 

 derived directly from the cell-substance, and it is, therefore, 

 not unlikely that the same takes place also under the above- 

 mentioned pathological conditions. 



At one time I was not disinclined to derive some of the 

 young buds of the omentum of rat, represented in figs, i and 

 ii, from peculiar large migratory cells, which seem to occur 

 only in the omentum of white rats. They are conspicuous by 

 their large size, their coarse granulations, which staine 

 very deeply in haematoxylin, and also, but to a less degree, in 

 carmine, and by their clear round nucleus, which was not, 

 however, stained with the above reagents ; and in this respect 

 alone they differ markedly from the other cellular elements 

 of the membrane. These migrants are found in considerable 

 numbers among the cell-accumulations around the large 

 blood-vessels, whence they may be traced into the smaller 

 trabeculae of the fenestrated portion. At some places these 

 cells are changed into fat-cells. 



As I said before, I was at first inclined to assume that 

 some of our buds are derived from these large migrants, 

 especially those figured in i and ii, by assuming that their 

 coarse granulations gradually disappear, and that also their 

 substance undergoes the above-described alterations, but 

 not being able to find intermediary forms I cannot support 

 that assumption. 



Before concluding this part of the paper I wish to mention 

 the changes that are observable in the nuclei of the surface 

 endothelium of the fenestrated portion of the omentum of 

 rat, consisting in this : — Amongst the ordinary oblong nuclei 

 of the ordinary endothelial cells (like those represented in 

 figs, i — v) there are seen occasionally oblong or round nuclei 

 [the ordinary nuclei are on the average about 00135 by 

 O'OOSl millimetres] considerably larger, even twice as large. 

 They show very otten constrictions, as if dividing, or are 

 nearly completely divided into two or even three smaller 



