272 
CHARLES F. DAWSON. 
months later the guinea-pig was chloroformed, it was found 
to be in an advanced stage of tuberculosis. The liver was 
greatly swollen and exhibited green and yellow necrosed 
areas. The spleen was enlarged about four times and was ex¬ 
tremely diseased. The omentum was the seat of an extensive 
infiltration of millet-seed-sized tubercles. The lymphatic glan¬ 
dular system throughout was also involved, the individual 
glands being enlarged from ten to twenty times, and upon sec¬ 
tion were found to be hard and gritty. 
It was also demonstrated by an experiment upon rabbits 
similar in plan to the foregoing, that hog-cholera can be trans¬ 
mitted by means of flies. 
Vegetable pathologists have shown that certain infectious 
plant diseases are distributed by insects. 
Several years ago, Mr. Waite, of the Department of Agricul¬ 
ture, called my attention to an experiment he was carrying on, 
in which he was repeating his former observations on the dis¬ 
tribution of the “ pear-blight ” organism. Near the pear tree 
upon which he was experimenting there was a bee hive. Cer¬ 
tain of the lower limbs of the tree had been inoculated with the 
“ pear-blight ” organism, and some of the upper limbs were pro¬ 
tected by mosquito netting. The bees could be seen visiting 
the trees, including the infected limbs. “ Pear-blight ” soon 
appeared in all the upper limbs not protected by the nettiug. 
Dr. Erwin F. Smith, of the Department of Agriculture, has 
shown in a bulletin on “ A Bacterial Disease of the Tomato, 
Egg-Plant and Irish Potato,” that the Colorado potato beetle is 
a factor in distributing that disease. Dr. Smith has also shown 
by control experiments that an infectious disease in cucurbits is 
distributed by certain living insects. The insects were sprayed 
with the liquid cultures of the bacillus ( B . tr acheiphihis) , and 
were then turned loose upon the plants. During a period of 
nine months in which the experiment was carried on, none of 
the plants which were protected by being covered with bell- 
glasses, became infected, while the unprotected ones succumbed 
to the disease. 
