LYMPHATICS OF SEROUS MEMBRANES. 271 



thoracic and abdominal surfaces of the centrum tendineum of 

 the Rabbit, Guinea-pig, Cat, and Man, fully to corroborate the 

 statements on the serous membranes made by v.Recklinghausen. 

 (See the woodcuts 57 and 58, in chapter viii. of this work.) 



According to Dybkowsky, the pleura costalis only possesses 

 lymphatics in the intercostal spaces, and where it is applied 

 to the musculus sterno-costalis. The capillary lymphatics 

 here form a close plexus, from which small trunks containing 

 valves arise, that run to the margin of the intercostal space. 

 The capillary plexus is for the most part arranged in two 

 layers, one of which is superficial, and occupies the fissures and 

 spaces of the matrix, their cavities being separated from that of 

 the pleura by the endothelium alone, and into which the sto- 

 mata found between the endothelial cells directly open (19); 

 whilst the other is more deeply situated, and separated from 

 the former by connective tissue, the fasciculi of which run 

 parallel to the plane of the pleura ; both layers intercommuni- 

 cate freely. The portions that cover the ribs themselves 

 possess no lymphatics. The mediastinum has lymphatics at 

 those points only at which adipose tissue intervenes between 

 its laminae. 



The lymphatic capillaries of the external lamina of the peri- 

 cardium form a close plexus lying near its inner surface, and 

 receiving serous canals from all parts of the matrix. According 

 to Ludwig and Schweigger-Seidel, we may distinguish in the 

 tendinous centre of the diaphragm of the Rabbit a system of 

 wide lymphatics that lie parallel to one another between the 

 fibres of the radiating layer, and are lined by endothelium; 

 they are covered by the basement membrane of the abdominal 

 surface, which consists of strong trabeculse corresponding to the 

 spaces intervening between the fissures, whilst from the latter 

 more delicate fasciculi arise, which form a delicate network 

 over the lacunae themselves (20). 



From these lacunas of the lymphatic system canals extend 

 towards the thoracic surface, where a close but delicate network 

 of capillary lymphatics exists between the pleura and the'cir- 

 cular layer. This plexus again pours its contents into wide 

 lymphatics provided with valves, that are likewise situated 

 on the thoracic surface. The plexus of capillary lymphatics 



