74 The MicrosGojpiG Germ Theory of Disease. By H. C. Bastian. 
myself with briefly summarizing the principal facts and arguments 
on which a judgment may be founded. 
1. The experiments of many investigators prove that the 
alleged causes of diseases may be actually introduced into the blood- 
vessels of lower animals by thousands without producing any dele- 
terious effects in a large proportion of the cases. 
2. Bacteria, if not actually to be found within the blood-vessels 
of healthy persons, do nevertheless habitually exist in so many 
parts of the body in every human being, and in so many of the 
lower animals, as to make it almost inconceivable that these 
organisms can be causes of disease. In support of this statement I 
have only to say, that even in healthy persons they may be found 
in myriads in and about the epithelium of the whole alimentary 
tract from mouth to anus ; they exist throughout the air-passages, 
and may be found in mucus coming from the nasal cavities, as well 
as in that from minute bronchi. They exist abundantly amongst 
the epithelial debris within the ducts of the skin, not only in the 
face, but in other parts of the body. Fresh legions of them are 
also being introduced into the alimentary canal with almost every 
meal that is taken, whence they may perhaps readily find their way 
into the mesenteric glands, if not farther within the system. And 
lastly, in persons with open wounds, bacteria are constantly to be 
found in contact with such surfaces, especially if the wounds are 
not well cared for, though the injured person does not necessarily 
suffer at all in general health. 
3. It is no answer to these difficulties to say that there are 
distinct species amongst these lower organisms, some of which are 
harmless, though others are poisonous (or so-called germs" of 
disease). In support of such opinion nothing can be alleged save 
some of the facts whose cause is doubtful ; whilst against such an 
interpretation may be brought the experiments of several investi- 
gators, showing that bacteria are the creatures of circumstance, 
and modifiable to an extraordinary degree. The last position is 
even admitted by Professors Sanderson and Lister. The former 
acknowledges that they are " the lowest organisms," and that they 
are " much more under the influence of the conditions under which 
they originate and are developed, than organisms of any other 
class ; " whilst Professor Lister's own work has compelled him to 
make an admission which, in the face of facts previously stated 
concerning the wide distribution of bacteria within the body, seems 
fatal to a consistent belief in the germ theory of disease. He says : 
" If the same bacterium may, as a result of varied circumstances, 
produce in one and the same medium fermentative changes differing 
so widely from each other, as the formation of lactic acid and that 
of black pigment in milk, it becomes readily conceivable that the 
same organism which, under ordinary circumstances may be com- 
