ON THE REAL NATURE OF DISEASE GERMS. 861 
lungs, or rising in a living state into the atmosphere from 
the sputum after its expectoration, are not great. At the 
same time neither circumstance can be regarded as impossible, 
neither view held to be untenable. 
The manner in which the bioplasm of tubercle multiplies 
may be studied in tubercular inflammation of the membranes 
of the brain : — The living matter may be seen extending 
round a small artery in the areolar tissue of the external 
coat. The living particles obstructed in the vessel make 
their way through its lining membrane and between the 
fibres of the muscular coat, until they reach the areolar 
tissue outside, where they grow and multiply. By their 
accumulation, the pressure upon the vessel becomes greater, 
and at last its calibre will be completely obliterated. From 
such tubercle collections minute germs may be readily de- 
tached, and after having found their way into a previous 
lymphatic vessel, or blood-capillary, might be carried to 
distant parts and grow there. In this way tubercles are 
formed in many different parts of the body and in the 
substance of many different tissues and organs. If a particle 
of fluid, holding tubercle germs in suspension, were intro- 
duced by inoculation into a healthy organism, the disease 
might be produced. 
Cancer Germs . — While it is almost certain cancer might be 
introduced by direct inoculation into the organism of a 
healthy person, many circumstances render it in the highest 
degree improbable that living germs detached from the 
growth could, under any circumstances, gain access to 
another organism through the air breathed, or in any other 
manner pass into the blood or tissues, as long as the surface 
remained uninjured. Cancer germs would probably live for 
some time in animal fluids out of the body, and it is by no 
means impossible that we may succeed in growing them in 
glass vessels away from their natural seat of growth, and 
watch the changes which occur under our microscopes ; but 
it is exceedingly doubtful if these germs would long retain 
their vitality if removed from the fluid which nourished 
them. 
Between the cancer germ, which cannot be conveyed by 
the air from the diseased organism to one not infected, and 
the germ of scarlatina, which will retain its vitality for weeks 
after it has escaped from the organism in which it was pro- 
duced, and may readily gain access to healthy organisms in 
the air they breathe, we have examples of living disease 
germs manifesting powers of retaining their vitality when 
free in many different degrees. In other words, these poisons 
