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THe MIcROSCOPE. 257 
sun, go into the meadow and attempt to swing a scythe all day 
and what will be the probable result? Let him of the north, 
change his habitation in summer to the tropical south, what may 
we expect ? 
Without further discussion we may say that certain kinds of 
bacteria cause disease by invading, against the provided defences, 
the bodies of animals or plants, and by physiological activities pe- 
culiar to themselves, disturb those of the invaded or parasitized 
hosts. In some cases their detrimental influences are mainly me- 
chanical. By multiplying and collecting in great numbers they 
form plugs in the blood vessels and impede the circulation. By 
similarly collecting in the air passages, suffocation may follow. 
Others, like the bacilli of tuberculosis, and typhoid fever, after 
gaining lodgement in the body, have a corrosive action by which 
the substance of the tissues is modified or destroyed, while still 
others give rise to chemical changes inimical to health. It has 
been found in certain cases, without, as well as within the living 
body, that organic compounds called ptomaines are formed (through 
the decomposing activities of special organisms), having physiolo- 
gical properties similar to those of the alkaloidal poisons. There 
is surely nothing surprising in this. The alkaloidal poisons like 
atropine and strychine are products of plant physiology. 
Should we wonder that among the multitude of chemical changes 
set up by bacteria in organic bodies. some of these should 
result in poisons as deadly as those secreted in other plants? More 
recently it is announced that poisons are manufactured in the 
chemical changes produced by the forces of the living body itself. 
To distinguish these the name leucomaincs has been given them by 
Gautier, their discoverer. Here again there is to my mind nothing 
improbable or contradictory to former thought. Green plants de- 
velop poisons, bacteria develop similar poisons as organic com- 
pounds; why need we wonder that we ourselves having wonderful 
vital powers over chemical changes may in some conditions and 
circumstances also give rise to poisonous products? 
What concerns us most is that the poisonous ptomaines may 
be produced in materials intended for human food, and thus make 
untold mischief and suffering. A case of this kind undoubtedly 
occurred in the dried beef poisoning reported to this society last 
year by Dr. Detmers. | 
