148 DR. E. RLEIN AND PROFESSOR BURDON SANDERSON. 



neigliboLirliood of the stomata and pseiido-stomata. Near 

 the ti'ue stomata are seen swellings and buds formed by the 

 proliferating endothelial cells, which project above the sur- 

 face and form in their first stage of development a sort of 

 wall round the stoma, so that the channel connected Avith 

 the opening looks as if lengthened, or, when further deve- 

 loped, forms a hollow cone. 



In some cases of chronic inflammation similar changes are 

 found on the pleural side to those already described on the 

 abdominal side, the endothelium here also showing prolifera- 

 tion round the pseudo- stomata. The system of plasmatic 

 canal- cells is also found to be altered in the same manner 

 as lately described by Hansen in the case of the cells of 

 the cornea, a process of which some indication may be found, 

 as stated above, even under normal conditions in certain 

 parts. The cells first appear to enlarge, their protoplasm 

 becomes distinctly granular, the nucleus becomes clearly 

 defined and is marked with depressions. In the next place, 

 the processes also begin to grow, and the body of the cell 

 with its processes splits up into single celhilar laminse. 

 We then have rows of cells arranged more like endothelium, 

 in which the individual cells are separated from one another 

 by narrow lines of cement. Another change, however, soon 

 takes place, which can hardly be paralleled in normal con- 

 ditions, namely, that buds begin to grow from particular 

 points of the body or processes of the cell which then 

 separate themselves as young cells. 



In some chronic inflammations, such as artificial tubercu- 

 losis, the plasmatic canal-cells may be seen to form nodes and 

 plates by proliferation ; this occurs at places where there is 

 at the same time superficial inflammation. 



The question arises where these young cells, Avhich are met 

 with in limited number rinder normal conditions, but under 

 pathological conditions in considerable numbers, both in 

 lymphatic vessels and in the plasmatic canals, originate. 

 It is certain that a large proportion of them may be regarded 

 as derived from the proliferating endothelial cells in the 

 neighbourhood of the true stomata and jaseudo-stomata, as 

 well as from the plasmatic canal-cells, while some are sucked 

 in from the abdominal cavity. 



These conditions will be referred to again in speaking of 

 the omentum, where they can be investigated with greater 

 precision . 



II. Omentum and Mediastinal Pleura. 

 a. Normal conditions. 



