2 ? 8 



greatly in the different animals. Around vessels of normal ani- 

 mals the localisation of the colonies was such that some 

 attraction seemed to have been exercised by the endothelium 

 on the bacteria. Very often too the spreading of the colonies 

 in the agar was quite regular, but sometimes the bacteria 

 seemed to have had some preference for the endothelium. More 

 can be said of the sections through the vessels of septicaemic 

 animals. Here within 24 hours the endothelial cells are changed 

 into one thick mass of bacteria. No separate colonies are to 

 be seen. In the surrounding agar the colonies appear at regular 

 distances. Now what is the reason that there are so many 

 bacteria on the endothelium? One feels inclined to think of 

 some Chemotaxis. But there is no doubt that this sort of endo- 

 thelium is a splendid medium for the bacteria. Quite a different 

 aspect again is offered by the sections through the vessels of 

 the immunised animals. Here too we find colonies spread 

 regularly through the agar but two things are very peculiar. 

 On the outer side of the vessel fairly many colonies have grown- 

 practically none on the endothelial side. And often there exists 

 all along the endothelium a zone where no colonies have grown. 

 So these experiments too prove that the endothelium of blood- 

 ressels has a very different influence on bacteria. At one time 

 it is an excellent medium for bacteria, at another no bacterium 

 can live on it. What the "normal" condition is, is hard to say. 

 Only the extreme positions are clear, in immunity we find the 

 endothelium in a condition most unfit for bacterial cultures, and 

 in septicaemia the opposite is the case. 



With these observations and experiments I hope to have 

 contributed to the acknowledgement of the importance of the 

 endothelial cells for processes of immunity and septicaemia. 



