270 SEROUS MEMBRANES, BY E. KLEIN. 



cells with rounded or oblong nuclei (frequently intervening 

 between the straighter fasciculi of connective tissue of the 

 middle layer radiating and concentric layer of the centrum 

 tendineum, the deeper layers of the intercostal pleura, the outer 

 lamina of the pericardium and of the dura mater) ; and lastly, 

 vagrant or migrating cells. In many Yertebrata the tissue 

 of the peritoneum contains isolated and retiform fasciculi of 

 smooth muscular fibres ; these are especially abundant in the 

 mesentery of the Triton and of the Frog. They are less nume- 

 rous in Mammals, though even here there are certain regions 

 where they are present in considerable abundance, as in the 

 peritoneal investment of the stomach of the Rabbit. 



The examination of the fibrous elements of the serous mem- 

 branes may best be conducted on thin sections (as of the 

 pleura, 14, and diaphragm, 15) that have been hardened in 

 chromic acid, or by means of surface views of portions of the 

 membranes (mesentery, pericardium), either in the fresh state, 

 or after having been previously macerated in bichromate of 

 potash. For the study of the cellular elements we possess 

 an admirable agent in chloride of gold, though here also the 

 examination of fresh preparations must not be neglected. 



c. LYMPHATICS. 



The presence of lymphatics in the connective tissue of serous 

 membranes was called in question by Dybkowsky. Schweigger- 

 Seidel, and Ludwig and Schweigger-Seidel, butBohm discovered 

 them upon the inner surface of the dura mater ; later inquirers 

 also consider the statement made by Schweigger-Seidel (13), 

 that the appearances of lymphatics is the result of manipulation 

 in an albuminous layer of cementing tissue between the endo- 

 thelium and matrix, is negatived by the fact, which indeed is 

 perfectly true, that in some cases the endothelium may be seen 

 to be completely preserved over the appearances of lymphatics 

 presented by the matrix. I am able, personally, so far as 

 regards my own observations on serous membranes, namely, 

 upon the mesentery of the Triton, Frog, Rabbit, Guinea-pig, 

 Cat, and Man ; the parietal layer of the Peritoneum of the Frog, 

 Rabbit, and Man ; the pericardium, pleura, and upon both the 



