POLYMORPHISM OF MICROBES. 279 



thus obtained the formation of small metastatic 

 centres in the kidneys, liver, lungs, etc. The spores 

 sent forth hyphae which were able to produce im- 

 perfect organs of fructification, but failed to effect 

 the formation of fresh spores. Gaffky, Koch, and 

 Leber repeated these experiments, and showed that 

 the acclimatization of any kind of mould in the 

 interior of the system was impossible, whatever might 

 be the more or less serious lesions produced by the 

 introduction of foreign bodies into the blood of a 

 warm-blooded animal. 



Errors caused in Laboratory Experiments by the 

 Involuntary Mixture of Different Microbes. We 

 should be the more cautious about accepting the real 

 or apparent polymorphism of certain microbes, since 

 the most scrupulous precautions do not always suc- 

 ceed in preventing confusion. Of this Klein gives 

 the following instances. 



While he was studying the microbe of anthrax in 

 his laboratory at the Brown Institution, one of his 

 friends was studying canine distemper in an adjoining 

 room. This friend injected the blood of a dog affected 

 by distemper into a guinea-pig's veins, and was sur- 

 prised to see the animal die two days later with all 

 the symptoms of anthrax, and to discover Bacillus 

 anthracis in its blood. Yet he had made the injec- 

 tion with a perfectly new hypodermic syringe ; while 

 Klein, for his own injections, had made exclusive use 

 of pipettes drawn to a point in the flame of a lamp. 



