REMARKS ON MICRO-ORGANISMS. 
849 
called w r oolsorters’ disease, in the North of England. The 
Bacillus anthracis is a large form of bacterium, as is shown 
at a in the accompanying woodcut. It is there shown 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 
method 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 absorbed 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 instru¬ 
ment, 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 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 antliracis 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 h, drawn on the same 
scale as a , where it is seen that the diameter can only be 
represented by a slender streak not one eighth of the diameter 
of the Bacillus anthracis , and such as, before the introduction 
of Koch’s method, would have escaped notice altogether. 
Now, this disease is totally distinct from pyaemia, being not 
accompanied with multiple abscesses or embolism; and thus 
it has been shown by Koch that septicaemia may exist as a 
deadly blood-disease, caused by the development of micro¬ 
organisms, being equally distinct from pyaemia and from the 
chemically toxic effects of septic products. 
On some occasions, as the result of the introduction of 
