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Tae MICROSCOPE. 51 
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an outer vascular layer containing a number of blood ves- 
sels held together by white, fibrous tissue; (2) a middle layer 
of white fibers containing large quantities of elastic tissue; (3) a 
layer of soft, delicate, nucleated cells, the osteoblasts. The perios- 
teum is firmly bound down to the bone by means principally of fibro- 
elastic septa, which are given off from its middle layer and penetrate 
far into the bone substance. These septa are called the perforating 
fibers of Sharpe. They are often accompanied by a blood vessel, 
and in the deeper portions are calcified like the lamellz, between 
which they penetrate. They may be studied in cross sections “of 
bone which have been decalcified. 
Beavieh Osea 
HOW DO MICRO-ORGANISMS PRODUCE DISEASE? 
ICROSCOPICAL science and experimental bacteriology have. 
demonstrated the etiological relation of micro-organisms to 
certain of the infectious diseases, and it is not improbable that fuller 
observations and experiments will discover the specific microbe of all. 
Having demonstrated this fact, insatiable scientific thought 
demands an answer to the question, how do these organisms induce 
disease? Why is it that after the entrance, development and mul- 
tiplication of, for example, the typhoid bacillus there is produced 
in the infected individual the clinical picture that the phys 
recognizes as typhoid fever? ’ 
Various theories have been offered to explain the phenom- 
ena of the specific diseases. It has been held that (1) the 
microbes produce disorganization of the blood; (2) that they collect 
in the vessels and there produce mycotic thrombi or emboli and thus 
interfere with the functions of, or totally destroy the organs of the 
body; (8) that they consume the proteids of the body; and (4) that 
they destroy the blood corpuscles. 
These theories have not borne the scrutiny of rigid scientific in- _ 
quiry, and further investigation has led to the belief that the 
symptoms of the infectious diseases are caused by the circulation in 
the blood of chemical poisons generated in the body by the develop- 
ment and multiplication of the specific micro-organism. 
Under the influence of bacterial life, complex animal tissues are 
split up into simpler substances, and the process goes on until the 
ultimate products of organic decomposition, carbon di-oxide, water 
