INVISIBLE ASSAILANTS OF HEALTH. 813 



The means of aggression or defense, as well as of sustenance, 

 of the phagocyte, is by attaching itself to a particle of matter, 

 and gradually surrounding and incasing it in its membranous 

 walls until it is literally swallowed. If the particle should be a 

 microbe, rich in protoplasm, it would be digested by the vora- 

 cious and omnivorous phagocyte ; but if of mineral origin, as dust 

 of coal or sand inhaled by the lungs, it would be carried to the 

 surface or to a safe receptacle, where the cell, having performed 

 its mission, deposits itself, still incasing its burden. The phago- 

 cytes seem to meet whole broods of infective microbes which may 

 have invaded the body, and destroy them, and, as it were, gradu- 

 ally acquire and permanently retain such efficiency as in future 

 invasions of the same species to prevent any harmful action. 

 The contest between these opposing forces does not always ter- 

 minate with regularity as to time, as in the acute infectious 

 diseases, but may become chronic, and the time and result un- 

 certain. 



In the slow, malarial diseases, according to this theory, the 

 phagocytes finally acquire a domination more or less complete 

 over the Bacilli malarial ; and this occurs not because the mala- 

 ria has become less virulent, but because the phagocytes have 

 acquired unwonted potency during the contest. This acquired 

 domination of the phagocytes over one species of microbe seems 

 not to be available against the inroads of other species. The 

 exemption acquired in diphtheria and some other diseases seems 

 partial as to degree and uncertain as to time. 



One dreadful example of the failure of self-limitation of dis- 

 ease is found in hydrophobia. Here there is no natural stay or 

 check to its fatality, and, although the most distinguished pa- 

 thologists have given this question their best attention for many 

 years, it seems questionable whether any life has ever been saved 

 from hydrophobia. Large numbers of persons have been treated 

 by inoculation for supposed hydrophobia, many of whom died, 

 and the symptoms proved the hydrophobic cause ; while in those 

 who recovered no positive demonstration of true hydrophobia 

 could be made, and the question of curability or prevention by 

 inoculation remains undetermined. 



M. Pasteur, the wizard micrologist, claims success in his bat- 

 tles with the rabies germs, and his brilliant achievements in other 

 fields lend encouragement to expectant humanity. Jenner's vac- 

 cine discovery, by which millions of lives have been saved, 

 encourages the sanguine belief that the principle of inoculation 

 will, ere long, be made available for the preservation of countless 

 human lives. 



The method of M. Pasteur has been to obtain some of the 

 positively fatal virus from the brain of a person or animal which 



