I possibility of the conveyance of the infection through an interme- 
j ’ diary host, such as arthropods or biting insects. 
j A favorite theory many years ago was that the disease is produced 
■ by a gas or miasm rising from the earth in the affected region. The 
I gas was supposed to be generated by earth or vegetation. At the 
I present day, no discussion of this theory is necessary. 
1 Trembles was early recognized to have some of the features of in- 
I fectious diseases. In 1843, Heeringen wrote “ I am compelled to be- 
, lieve that trembles belongs to the anthrax family.” This was twelve 
ij; years before the discovery of the anthrax bacillus. Mention is fre- 
|| quently made of the fact that the disease may be carried from one 
:B animal to another by feeding the flesh of a diseased animal. 
In 1877, Philips reports finding “ spiral bacteria ” in the blood of 
i a typical case, and the same organism, with cocci, in the urine of the 
II same case. He encountered similar organisms in the urine of other 
I cases. 
I Gardner (1880) reported finding in the blood of a heifer suffering 
i; from the trembles, organisms “ that bore in size and behavior a 
i striking resemblance to the form of bacteria called by naturalists 
! bacilla subtilissima.” He found the same organism in the water of 
|j a spring that had supplied a family in which milk sickness was pres- 
f| ent. Dogs suffering from “ slows ” acquired by eating the flesh of the 
‘f heifer also had the organism in the blood. He also found the organ- 
p ism in milk. 
I Graff (1841) reported some very remarkable experimental work 
f with trembles. He found the flesh of the animals not to differ mate- 
[ rially in appearance from that of sound animals. Salting meat, he 
! says, does not impair its poisonous properties. The milk of a cow 
was poisonous, as shown by feeding it to dogs for eight days after she 
was removed from the infected pasture; but a test made a week later 
showed the milk to be harmless. He found small amounts of meat or 
butter sufficient to cause the disease. “ One ounce of butter or cheese 
or 4 ounces of beef, either raw or boiled, administered three times a 
day, will certainly prove fatal within six days, and often earlier.” 
All these experiments were upon dogs and the flesh of his experi- 
mentally killed dogs was as poisonous as the beef that conveyed the 
disease. 
Graff found that treating the flesh with dilute sulphuric acid for 
two hours did not destroy the poison; even heating had no effect. 
He says butter heated “ to such a degree as to cause it to inflame lost 
none of its poisonous properties.” He failed to extract the poisonous 
agent from meat by prolonged boiling. He failed in attempts to 
communicate the disease “ by an inoculation with any portion of the 
body or secretions from infected animals.” These experiments lack 
confirmation. 
