On Immunity loith Special Reference to Cell Life. 441 



and is therefore used as a lightning conductor. Great masses of 

 iron present in buildings gi^e rise to, or increase, the risk of their 

 being struck by lightning, and the metal only becomes protective 

 against lightning when it is so employed that the electricity is con- 

 ducted away outside the building. It would never occur to anyone to 

 speak of great masses of iron machinery present in buildings as if they 

 were lightning conductors. It is equally unreasonable to speak of 

 the antitoxic property of the brain cortex, in which the toxophile 

 groups are present in great quantity, but also retain their relations 

 with the nerve-cells. When this really considerable misunderstand- 

 ing is eliminated from Roux's results these become entirely confirma- 

 tory of my views, and it is difficult to understand how, subsequent 

 to Weigert having placed the matter in so clear a light, the beautiful 

 experiments of Roux can be utilised by another eminent authority 

 as a means of combating my theory. 



Much more complex than in the cases hitherto discussed are the 

 conditions when, instead of the relatively simple metabolic products 

 of microbes, the living micro-organisms themselves come to be con- 

 sidered, as in immunisation against cholera, typhoid, anthrax, swine 

 fever, and many other infectious diseases. There then come into 

 existence alongside of the antitoxines, produced as a result of the 

 action of the toxines, manifold other reaction products. This is 

 because the bacterium is a highly complicated living cell, of which the 

 solution in the organism yields a great number of bodies of different 

 nature, in consequence of which a multitude of " Antikorper " are 

 called into existence. Thus we see, as a result of the injection of 

 bacterial cultures, that there arise alongside of the specific bacterioly- 

 sines, which dissolve the bacteria, other products, as, for example, 

 " coagulines " (Kraus, Bordet), i.e., substances which are able to cause 

 the precipitation of certain albuminous bodies contained in the 

 culture fluid injected; also the so-much discussed " agglutinines " 

 (Durham, Gruber, Pfeiffer), the antiferments (von Dungern), and no 

 doubt many other bodies which we have not yet recognised. 



It is by no means imlikely that each of these reaction products 

 finds its origin in special cells of the body ; on the other hand, it is 

 quite likely that the formation of any single one of these bodies is 

 not of itself sufficient to confer immunity. Thus in case of the intro- 

 duction of bacteria into the body we have to do with a many-sided 

 production of different forms of " Antikorper," each of which is 

 directed only against one definite quality or metabolic product of 

 the bacterial cell. Accordingly, in recent times, the practice of using 

 for the production of immunisation definite toxic bodies isolated from 

 the bacterial cells has been more and more given up, and for this 

 purpose it is now regarded as important to employ the bacterial cells 

 as intact as possible. The beautiful results obtained for plague by 



