282 Dr. Edward E. Klein [Feb. 20, 



theria, like typhoid fever or scarlet fever, can be, and, as a matter of 

 fact, is, often conveyed from an infected source to great distances by 

 the instrumentality of milk. In malignant anthrax, another disease 

 in which the contagium is conveyable by direct contact, e. g. in the 

 case of an abrasion or wound on the skin coming in contact with 

 the blood of an animal dead of anthrax, we know that the spores 

 of the anthrax bacilli can be, and, as a matter of fact, in many 

 instances, are, conveyed to an animal or a human being by the air, 

 water, or food. The bacilli of tubercle, finding entrance through a 

 superficial wound in the skin or mucous membrane, or through 

 ingestion of food, or through the air, can in a susceptible human 

 being or an animal produce tuberculosis either locally or generally. 

 The difference as regards mode of spread between different diseases 

 resolves itself merely into the question, which is, under natural con- 

 ditions, the most common mode of entry of the disease germ into the 

 new host ? In one set of cases, e. g. typhoid fever, cholera, the 

 portal by which the disease germ generally enters is the alimentary 

 canal ; in another set an abrasion or wound of the skin is the portal, 

 as in hydrophobia, tetanus, and septicaemia ; in another set the respi- 

 ratory organs, or perhaps the alimentary canal, or both, are the paths 

 of entrance of the disease germ, as in small-pox, relapsing fever, 

 malarial fever ; and in a still further set the portal is just as often 

 the respiratory tract as the alimentary canal, or a wound of the skin, 

 as in anthrax, tuberculosis. But this does not mean that the virus 

 is necessarily limited to one particular portal, or that it must be 

 directly conveyed from its source to the individual that it is to 

 invade. All this depends on the fact whether or not the microbe 

 has the power to retain its vitality and virulence outside the animal 

 or human body. 



Anthrax bacilli are killed by drying ; they gradually die off if they 

 do not find sufficient nutriment in the medium into which they happen 

 to be transferred ; they are killed by exposure to heat far below 

 boiling-point ; they are killed by weak carbolic acid. But if these 

 anthrax bacilli have been able to form spores, these latter retain their 

 vitality and virulence when dried, when no nutriment is offered to 

 them, and even when they are exposed for a few seconds to the heat 

 of boiling water, or when they are exposed to the action of strong 

 solutions of carbolic acid. Similarly, the bacillus of dii^htheria is 

 killed by drying, also by weak solutions of carbolic acid ; it is killed 

 when kept for a few days in pure water, on account of not finding 

 sufficient nutriment ; fortunately the diphtheria bacillus is killed in a 

 few minutes at temperatures above 60° or 65° C, for this bacillus 

 does not form spores. The same is the case with the microbe of 

 scarlet fever. 



The tubercle bacillus forms spores ; these are not killed by 

 drying, they are killed by the heat of boiling water of sufficiently 

 long duration, two or more minutes ; they arc not killed by strong 

 carbolic acid. 



