204 On the Real Nature of Disease Germs. — [Mpnthly, Microscopical 
Living tubercle germs will not be considered as very closely 
related to the contagious particles which are the active agents in 
the propagation of contagious fevers. There is, however, reason to 
think that particles of living growing tubercle exist sufficiently 
minute to be supported by the atmosphere and carried long dis- 
tances; while there are many facts which are considered by some 
sufficiently conclusive to justify the opinion that tubercular disease 
of the lungs is at least in some instances contagious. And it is 
certain that the most recent observations in connection with the 
subject of the nature and mode of propagation of tubercle, so far 
from militating against this view, tend rather to support it. That 
tubercle is not eminently contagious is certain, while the proba- 
bilities of minute particles of living growing tubercle escaping into 
the air while it remains in the air-cells of the lungs, or rising in a 
living state into the atmosphere from the sputum after its expec- 
toration, 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 liming membrane and 
between the fibres of the muscular coat, until they reach the areolar 
tissue outside, where they grow and multiply. By their accumu- 
lation, the pressure upon the vessel becomes greater, and at last its 
calibre will be completely obliterated. From such tubercle collec- 
tions minute germs may be readily detached, and after having found 
their way into a pervious 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 introduced 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 impro- 
bable 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. 
