THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 331 
rium, as is shown at @ in the accompanying woodcut. It is 
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there represented magnified 700 diameters, along with red 
blood-corpuscles of a mouse, and the rods of which it is 
composed are seen to be in diameter nearly one fourth of 
that of the red corpuscles. Koch’s method of staining the 
sections shows in the most beautiful manner that these 
bacilli are not only present in the spleen and some other 
organs, but that they people the blood in the minute vessels 
of all parts. Koch has thus added to our conviction that 
the bacillus is the cause of the symptoms, seeing that, as he 
remarks, it is impossible to suppose that an organism can 
develop in such enormous numbers at the expense of the 
vital fluid without exerting a serious influence upon the 
system. 
But the most striking and important results of Koch’s 
methods of investigation are those which relate to organisms 
of much smaller dimensions. He found that, if putrid 
liquid is injected under the skin of a mouse, the animal 
may die in the course of a short time, as the result of the 
chemically toxic effects of the products of putrefaction ab- 
sorbed into the circulation; but, if it survive this primary 
disorder, it may succumb in the course of about two days to 
blood disease. If the point of a lancet be dipped into the 
blood of the heart of a mouse which has died in this way, 
and a scratch be made in the skin of a healthy mouse with 
the envenomed instrument, the second mouse dies with 
similar symptoms to those of the first, the poison being 
absolutely certain in its virulent operation; and the same 
thing may be continued indefinitely through any series of 
animals. If now sections of the tissues be made and stained, 
and examined by Koch’s procedures, it is found that the 
entire blood of the diseased animal is peopled with bacteria, 
resembling those of the Bacillus anthracis in the enormous 
multitudes in which they are produced, and also in their 
rod-like form, but differing from them in being exquisitely 
minute and delicate, as is shown at 6 (drawn on the same 
scale as @, as is indicated by the accompanying outlines of 
red corpuscles), where it is seen that the diameter can only 
