BY DR. KLEIN. 45 



from the aperture. Sucli an arrangement we find on the por- 

 tions' of the abdominal side of the diaphragm, which corre- 

 spond to the so-called lymph channels, on certain parts of the 

 mesentery, and very abundantly in the pleura and omentum 

 on the structures already mentioned as resembling lymph fol- 

 licles. They are distinguished by the name of tilomata, and 

 are looked upon as the recipient openings of canals which be- 

 long to the lymphatic system. In the case of many of these 

 cells this has not yet been proved ; some of them have even 

 been regarded as small endothelial portions of larger cells ; 

 while others give the impression of being accidental forma- 

 tions. Of such openings, or stomata^ those that occur on the 

 * septum of the cisterna lympliatica magna of the frog may 

 serve as the type. If we cut out this membrane from a frog 

 or toad, spread it out and mount it in a solution of common 

 salt, or in serum, or if instead we first color it in silver and 

 then mount it in glycerine, we shall find a proportionately 

 large number of roundish or oblong openings between large 

 radiating endothelial cells. These discontinuities represent 

 the openings to short canals, which pass through the mem- 

 branes and connect the abdominal cavity with that of the 

 cisterna lymphatica magna. These openings are bordered by 

 small granular cells, the convexities of which project into 

 them. They are compactly arranged together, and each pos- 

 sesses a roundish nucleus. If the spreading out of the speci- 

 men has not been accomplished with sufficient care, or the 

 membrane is too much shrunk, we miss the above-mentioned 

 regular openings, and there appear instead only groups of 

 small roundish cells i.e., the openings are collapsed, and the 

 cells which line them have approached each other, so as to 

 come in contact. The nature of the small bodies which pro- 

 ject in the interior of the stomatr has been disputed. It has 

 been believed that they are nothing more than the nuclei of 

 the large radiating endothelial cells which surround them. 

 But, as we may convince ourselves both in fresh and in silver 

 preparations, they are really endothelial cells seen in profile, 

 which line the apertures. In female frogs and toads these 

 cells are provided with cilia. In the chapter on lymphatic 

 vessels we shall have an opportunity of making several addi- 

 tional remarks on the stomata. 



We shall, in conclusion, endeavor to show that the lines 

 which are brought out by nitrate of silver in the serous mem- 

 branes are caused by precipitations for the most part in the 

 albuminous substance which connects the cells, and not merely, 

 as many authors believe, in an albuminous fluid which col- 

 lects between their surfaces. A serous membrane prepared 

 from an animal just killed may be spread upon a cork plate 

 and rinsed with one per cent, solution of sugar, or with a very 



