236 DR. E. KLEIN. 



vestigation. The omentum is carefully removed from the 

 freshly killed animal; in the case of mouse, rat, guinea-pig, 

 and rabbit, the omentum, together with stomach, pancreas, 

 and spleen, is removed from the animal under fluid ; in the 

 case of dog or cat a portion of the omentum can be simply 

 cut off and placed in the proper fluid. This is in all cases a 

 2 per cent, solution of bichromate of potash. The omentum is 

 kept in this fluid for from one to two weeks ; small portions of 

 it are then washed thoroughly in water, and stained in 

 haematoxylin, or better first in carmine and then in hsemato- 

 xylin. 1 shall have occasion hereafter to point out the ad- 

 vantage of this double staining. The stained preparations 

 are finally mounted in glycerine. 



1. Examining carefully the fenestrated portions of the 

 omentum of a full-grown rat, larger or smaller bud-like pro- 

 jections are found on tlie bundles of connective tissue forming 

 the trabeculse of the fenestrse. These buds are covered 

 with the same endothelium as that lining the trabeculae (see 

 figs, i — v) ; they are not as a rule in connection with the 

 connective-tissue bundles, except in later stages, where the 

 content of the buds becomes itself fibrillar tissue. As regards 

 the size, they vary very much. Those represented in figs. 

 i — V are all relatively small, but there are others twice, thrice, 

 and even more times as large as that represented in fig. iv 

 or fig. V. The smallest buds are those in figs, i and ii ; 

 they are either pear-shaped, and by their stalk attached to 

 the trabeculae, or they are conical with very broad basis, by 

 means of which it rests on the connective-tissue bundle. An 

 interesting form is presented by some of them being of more 

 irregular form and of a plate-like extension, with one or 

 more spindle-shaped thickenings (seefig. iii). In the young 

 stages the buds are composed, besides the covering endo- 

 thelium, of a substance which is very indistinctly granular, 

 andwhich stains, somewhat like theconnective-tissuebundles, 

 conspicuously in carmine ; the endothelium, on the other 

 hand, has a greater aflfinity to haematoxylin, and hence the use- 

 fulness of staining the preparation in carmine and in haema- 

 toxylin. But while the bud-like structures have a greater 

 affinity to carmine than to hseniatoxylin they are not alto- 

 gether indifferent to the latter; this is especially the case 

 with the larger examples that we find in the more dense part 

 of the fenestrated portion, for these assume a peculiar purple 

 colour which makes them very conspicuous among the rest 

 of the tissue, and under these circumstances are very easily 

 distinguished. Not all buds contain, or rather are composed 



