December 16, 1904.] 



SCIENCE. 



819 



may well claim attention in many work- 

 shops- of science. 



The short time at my disposal does not 

 permit a wide survey of the field of bacteri- 

 ology, and I have deemed it best to discuss 

 in a general way the parasitism of bac- 

 teria and to outline the probable results of 

 any attempts of medical and sanitary sci- 

 ence to modify this parasitism. In under- 

 taking this task I have adopted the some- 

 what discredited method of presenting ac- 

 tual hypotheses, partly new, partly old, in 

 a new dress. These furnish a definite point 

 of attack, and are better suited for discus- 

 sion than any presentation which boxed the 

 compass with the views already well known. 



Infectious diseases have frequently been 

 portrayed as a battle between two organ- 

 isms, the host, on the one hand, the parasite, 

 on the other. There are few diseases even 

 among those not strictly infectious in char- 

 acter in which this battle does not go on at 

 some stage and in which the activity of 

 bacteria may be ignored. For some years 

 the analysis of this warfare has been the 

 chief problem of bacteriology and pathol- 

 ogy. What are the weapons of offense and 

 defense on either side? Are the weapons 

 simple or complex? Are they changed as 

 the struggle progresses to suit the imme- 

 diate state of the battle? Do the combat- 

 ants themselves change during long or short 

 periods of time, and does the character of 

 the disease change as a consequence? Do 

 ■the parasites act differently when posing 

 for us in the culture tube than in the ani- 

 mal body? These and other queries may 

 easily be read into the special literature of 

 the last decade. 



To realize the great complexity of this 

 struggle we need but to review the gross 

 facts of disease which express themselves 

 in epidemics, on the one hand, in individual 

 disease, on the other. We meet all grada- 

 tions of severity, from rapid death to a 

 mild transient disturbance, from a disease 



lasting hours to one lasting fifteen or 

 twenty years, or even longer. Even the 

 simplest generalizations concerning such a 

 varied phenomenon must necessarily be 

 subject to many exceptions, and perhaps 

 gross inaccuracies. This is evident from 

 the heated discussions which have been 

 waged over the humoral and the cellular 

 phenomena, the antitoxic and bactericidal 

 forces of the blood and the phagocytic ac- 

 tivities of certain cells, each party to the 

 discussion claiming, at least for a time, that 

 the opponent had no case. Though the 

 brilliant researches of Metchnikoff and 

 Ehrlich, and the fundamental discovery of 

 Behring and Kitasato, have to a certain 

 degree exposed the mechanism of warfare, 

 the exposure is only fragmentary, and the 

 hypothetic reconstructions based on it are 

 leading as usual to further controversy. 

 We do know that no two species of micro- 

 organisms carry on the warfare just alike, 

 and that the same parasite finds a some- 

 what different situation in every host at- 

 tacked. The problem of the immediate 

 -future is to determine where the brilliant 

 discoveries of Metchnikoff, Nuttall, Behr- 

 ing, Bordet, Ehrlich and others belong in 

 the life of each microbe, and to construct 

 for each disease the exact nature of the 

 contest. 



In the following pages I do not intend to 

 enter into any discussion concerning the 

 intimate life of bacteria, but simply to 

 point out certain biologic problems which 

 seem to lie on the surface, as it were, and 

 which illustrate the close relation existing 

 between bacteriology and general biology. 

 They have suggested themselves to me from 

 the comparative standpoint, one up to the 

 present biTt poorly cultivated in medical 

 science. 



The researches of Roux, Kitasato and 

 Behring, Van Ermengen and others, have 

 shown that certain species of bacteria se- 

 crete toxins during their vegetative period , 



