ocking of
shallow bodies of water with varieties of fish that feed upon the mosquito
larvae.

[Fig. 171]

Fig. 171--*Stegomyia*, the yellow-fever mosquito (after Howard).

*Yellow Fever.*--This scourge of the tropics is, like malaria, caused by
animal germs. It is also propagated in the same manner as malaria, but by
a different variety of mosquito (_Stegomyia_, Fig. 171). The stamping out
of yellow fever in Havana, the Panama Canal Zone, and other places,
through the destruction of this variety of mosquito, affords ample proof
of the correctness of the "mosquito theory."

[Fig. 172]

Fig. 172--*Consumption germs* from the spit of one having the disease.
Highly magnified and stained. (Huber's _Consumption and Civilization_.)

*Consumption*, or tuberculosis of the lungs, spoken of as the "white
plague," was among the first diseases shown to be due to bacteria.
Consumption is now recognized as an infectious disease, though not so
readily communicated as some other diseases. Several methods are
recognized by which the germs are passed from the sick to the well, the
most important being as follows:

1. By personal contact of the sick with the well, especially in kissing.

2. By the sputum, or spit, which, if allowed to dry, is blown about as
dust and breathed into the lungs(132) (Fig. 172).

3. By means of objects (drinking cups, tableware, etc.) that have been
handled by consumptives.

4. By infectious material associated with houses or rooms in which
consumptives have lived.

These methods of spreading consumption suggest the necessity for the
greatest care, on the part of both the patient and those having him in
charge.(133) The material coughed up from the lungs and throat should be
collected on cloths or paper handkerchiefs and afterwards burned. The
house where a consumptive has lived should be disinfected, repapered or
calcimined, and thoroughly cleaned before it is again occupied. The inside
woodwork should also be repainted. The approaches to the house where the
patient may have expectorated should be disinfected and cleaned. Since the
germs are able to live in the soil, fresh lime or wood ashes should be
spread around the doorsteps and along the walks.

*Typhoid Fever*, one of our most dangerous diseases, is caused by germs
(bacteria) that enter the body through the food canal. They attack certain
glands in the walls of t