3 8 THE POPULAR SCIENCE MONTHLY, 



the cause, or avoiding it in some way or other so that the body may 

 remain unaffected, (a) The antiseptic method introduced by Lis- 

 ter is a good instance of the methods which aim at destroying the 

 cause before it has acted, (b) Residence in high localities, drain- 

 age, etc., are instances of the methods by which the causes of dis- 

 ease may be so attenuated or diluted as to become harmless, (c) 

 Absolute cleanliness. Aseptic methods are based on the possi- 

 bility of avoiding certain causes entirely without destroying 

 them. 



2. Protection consists in so modifying the possible host as to 

 render it able to resist virulent parasites. This can be done either 

 by (a) increasing its strength and activity, as by diet, warmth, 

 functional activity, ( and other hygienic conditions (Wargunin) ; 

 (b) rendering its tissues and fluids unsuitable media for the 

 growth or full development of the parasite inoculation and Jen- 

 ner's vaccination are good instances of that method, which has 

 been further extended by Pasteur and others ; (c) by establishing 

 tolerance (Sewall, 1887). 



3. The curative methods consist in attenuating or entirely de- 

 stroying the virus causing the disease after it has penetrated into 

 the body, (a) The actual destruction of the parasite within its host 

 is apparently still a desideratum, (b) Attenuation of the virulence 

 can be obtained by introducing into the blood and tissues some 

 product either interfering with the full development of the para- 

 site or modifying the tissues and fluids of the body so as to 

 increase their resistance to the extension of the parasite or to its 

 products. This seems to be the chief principle at the root of 

 Pasteur's vaccination for hydrophobia, etc. (c) Neutralizing the 

 physiological action of the virus by using its physiological antag- 

 onist. Muscarine, for instance, may be antagonized by atrophine. 

 Lauder Brunton (1873) directed attention to the possibility of ap- 

 plying this principle to the treatment of cholera. (The same idea 

 has been applied to the treatment of poisoning by snake venom. 

 Wynter Blyth, 1877 ; Lacerda, 1881.) (d) Destroying and re- 

 moving the substratum or ground which has become contami- 

 nated by the parasite. This is apparently the view which Koch 

 has taken of the action of his lymph. The action of the prod- 

 uct on the tissues is, however, of the same "kind as that of the 

 substances used in some of the methods already mentioned, but 

 more intense, and Koch's views will probably have to be 

 modified. 



In this attempt to analyze the methods which have been pro- 

 posed I have separated processes, many of which may act concur- 

 rently. This is, however, of little consequence, for my object was 

 less to give an account of any single method than to trace the de- 

 velopment of the ideas which are at the basis of the treatment of 



