290 Dr. Edioard E. Klein [Feb. 20, 



one to three days, but it is not communicable to rabbits ; mice infected 

 with the tetanus bacilli and then injected with rabbit's blood do not 

 become affected with tetanus and remain alive.* 



While on the one hand, then, the tissue juices and the blood, 

 independent of the cellular elements, possess this germicidal action 

 — small or nil in susceptible, larger in animals less susceptible, and 

 largest in unsusceptible animals — there is, on the other hand, a con- 

 siderable body of evidence to show that the least germicidal action 

 seems to be possessed by those very cells themselves which figure in 

 the theory as the destroyers of Bacteria, as phagocytes; that is to 

 say, that of all the tissues the so-called phagocytes are the materials 

 offering to the Bacteria the best means of existence. Even in cases 

 in which the lymph and blood fluid have against particular Bacteria 

 the greatest germicidal power, the so-called phagocytes are for a time 

 the last refuges for the Bacteria. I will illustrate this by a number of 

 examples both of acute and chronic infectious diseases, as gonorrhoea, 

 Egyptian ophthalmia, Koch's mouse septicaemia, leprosy, and tuber- 

 culosis ; this latter is particularly instructive, as it demonstrates the 

 absurdity of the alleged phagocytosis of the cells of the spleen in 

 tuberculosis, for it is the latter cells in which the tubercle bacilli 

 thrive well, and which they choose pre-eminently. 



[4. Demonstration : tubercle cells and leprosy cells.] 



Nay, more than this : non-pathogenic Bacteria cannot exist in the 

 normal blood and in the tissues, in the wall of the alimentary canal, 

 in the tonsils, in the tongue ; they are destroyed and are therefore 

 absent in the living tissue. But they can, for a time at any rate, 

 exist in the cells of those parts, and in these, and these only, they 

 are met with ; these cells are therefore just the reverse of phagocytes, 

 being the last refuges of the Bacteria. 



These facts seem to show that cells containing in their substance 

 living Bacteria is no evidence whatever of a battle going on between 

 the cells and the Bacteria, but rather the reverse. The assumption 

 of the presence in the so-called phagocytes and similar cells of a 

 "defensive proteid" seems therefore oj^posed by these facts. The 

 cells seem to possess a particular chemical attraction for the Bacteria, 

 just as is possessed by certain chemical substances ; such attraction 

 is spoken of as positive chemotaxis in contradistinction to negative 

 cliemotaxis — that is, the opposite or repulsive interaction between 

 Bacteria and certain substances. This line of inquiry is of quite 

 recent date, and promises to produce important and interesting results. 



From all this we conclude, then, that in some cases the blood and 

 tissues are, or include, a natural antidote ; in others the antidote is 

 not present naturally, and is only furnished by the Bacteria them- 

 selv^es, and still in others the tissues, though possessed of this antidote, 

 may lose it owing to altered conditions. 



Another point worth considering is the peculiar inimical action 



* Behring and Kitisato, 'Deutsche Med. Woeh.,' 1890, No. 49. 



