28G Opinions on Epidemics and Epizootics. 



active state, but whether such cells,* or any portion of them, 

 floating about in the air, and taken into the lungs, or swallowed, 

 or permitted to adhere to the skin, is a real cause of the pro- 

 pagation of small-pox, no microscopist has yet ascertained. 



The probability of a scientific theory in any given state of 

 knowledge does not offer the slightest excuse for abstaining 

 from a rigid process of inquiry and verification, and those 

 accurate thinkers who consider Dr. Lankester's hypothesis may 

 be right, will not fail to perceive the want of decisive evidence 

 to support it. 



When Dr. Lankester asserts that small-pox can be com- 

 municated to suitable individuals by the process of inoculation, 

 he states a fact of which the proof is abundant ; but when he 

 takes small-pox as a type of epidemic diseases, and affirms 

 that they can only arise by the action of specific poisons, he 

 oversteps the limits of that which is known, and by implication 

 affirms divers theories open to doubt. We have already shown 

 that such a philosophy virtually affirms the original creation of 

 specific diseases, and it also affirms other theories which, if 

 less startling, ought not to be accepted lightly. In a natural 

 and healthy condition we find a continual formation of corpus- 

 cles, or cells, and such formations are by no means sharply 

 distinguished from all the products of disease. Causes, such 

 as temperature, moisture, dryness, the presence of putrefying 

 matter introduced into the system from extraneous sources, 

 may determine the production of morbid cells by simple 

 variation, from healthy cells, and without any hereditary 

 descent from other morbid cells of any particular kind. This 

 possibility is denied by those who account for diseases by 

 presuming them to result exclusively from specific poisons, 

 themselves the product of previous disease of the same 

 species. 



We do not offer any opinion as to the extent to which 

 physical and chemical agencies can modify healthy actions, so 

 as to convert them into morbid actions. No one will deny 

 that such an influence may be exerted to a large extent, and 

 no one is entitled to lay down any limits of such action, except 

 those which result from a rigid application of reasoning to a 

 sufficient group of ascertained facts. 



In the present state of science a certain class of diseases 

 are not unreasonably supposed to result from something like 

 an action of fermentation, and are hence called zymotic. Now, 

 the researches of microscopists, and especially of M. Pasteur, 

 lead to the belief that very minute organisms, more or less 



* In the wide sense now given to the term " cell," it may be used without 

 expressing any precise idea of its structure. 



