SHOWS THE CELL-STRUCTURE 9 



In the last chapter experimental evidence is given 

 to prove that blood-serum has an inhibitory action on 

 cell-division; and it will also be seen that it is pos- 

 sible to measure this inhibitory action. Since the 

 cell-proliferation of healing is * caused by chemical 

 substances contained in the soluble remains of dead 

 tissues, and since, as will be shown, bacteria decom- 

 pose these solutions, a field of research is opened for 

 the investigation of this decomposing action by various 

 pathogenic bacteria; for in decomposing the sources 

 of the causes of healing they greatly modify that pro- 

 cess, and the healing process must play an important 

 part in immunity against disease. Further, bacteria 

 may have an action on the substances contained in 

 blood-serum which restrain cell-division. We fear that 

 we have hitherto been able to do little towards the 

 investigation of this factor in the problem of immunity, 

 which is now mentioned for the first time. 



These are only a few of the fields which have been 

 pried into by experimentation with this new method. 

 It has been impossible for us to investigate all the 

 paths of research which have been opened up, and 

 prospective workers may be assured, from our own 

 personal experience, that research with stained living 

 cells will amply repay the time and patience expended 

 on it. 



For the examination of the arrangements of the 

 cells in living tissues we have not, so far, been able 

 to make this in-vitro method so useful as is the older 

 method of examining sections of dead tissues, but we 

 think that improvements may be possible. For blood- 



