252 THE MICROSCOPE. 
power of self-perpetuation or reproduction and multiplication, en- 
dowed with specific characteristics, and animated and controlled 
by a spark of that same mysterious quality or substance—which- 
ever it is—which distinguishes ourselves from the inorganic, dead 
clods of earth, the quality or substance known to us as vitality or 
life. Where this last comes from, and how it is associated with 
the minute speck revealed by our microscope, science cannot tell. 
Homogeneous immersion lenses fail utterly to give us instructions 
in this important particular. 
Not all communicable diseases are, however, due to bacteria. 
Scabies, or the “itch” of the olden time, is in consequence of an 
eight legged mite; some of the mold-like and yeast-like plants in- 
fest, to our discomfort, the human body; trichine and numerous 
other worms are causes of disease, and recently it appears to have 
been established that malaria is to be charged to the account of 
minute amceboid animals, making tenements of our blood corpus- 
cles. 
But making these and other exceptions, the bacteria may yet 
be said to be the disease producer, the parasites of contagious dis- 
eases, as well as many maladies not considered communicable. 
Whether tuberculosis (consumption) is always directly derived by 
contagion is not settled, though that the morbid processes are due 
to Bacillus tuberculosis, a specific and now well-known organism, 
ought to be universally accepted. The statistics of the hospitals 
do not yet show that this disease increases in consequence of the 
admittance of tuberculous patients. 
Whether or not tuberculosis as it exists, always passes directly 
from the diseased to the healthy, it is positively a virulently con- 
tagious malady, and the sooner this is recognized the better for 
human life and sanitary science. The disease can at any time be 
communicated by inoculation to healthy animals, and this from 
strictly pure cultures of the specific microbe. Keep this latter 
strictly away and we shall suffer no more from the peculiar and 
dreadful scourge which now inflicts such untold misery upon our 
race. As we come to know more about the various methods by 
which the virus is conveyed, we shall be better able to escape its 
contagion. It is now thoroughly demonstrated that tuberculosis 
may be conveyed through the food, a method, no doubt, which has 
obscured the real contagious character of the disease. 
