252 LEVINE: STUDIES ON PLANT CANCERS—IV 
Huytra (1905), in studying the effect of von Behring’s inoc- 
ulating fluid in immunizing cattle against Bovine tuberculosis, 
used 0.004-0.025 gm. of Bovine tuberculosis to produce this 
disease. Findel (1907) studied the difference between inhalation 
and feeding as methods for inducing tuberculosis. He used 
dogs, calves and guinea pigs. Like Preyss he calculated that 
by certain spray methods he was able to induce tuberculosis in 
the guinea pig with twenty tubercle bacilli and suggests that 
only one bacillus is sufficient to infect the guinea pig. Theobald 
Smith (1908) in studying Bovine tuberculosis, immunized cattle 
by injections of 5-300 mg. of dry weight of tubercle kacilli of 
the human of different ages. The number of individuals in 
these masses of bacteria was not estimated. 
Barber (1907), studying the transmission of the characters, 
size, and form in Saccharomyces anomalus, Bacillus coli communis, 
B. typhosus and B. megatherium, devised an isolation pipette 
whereby he was able to make a culture from a single cell. 
By this method he was also able to inoculate a mouse with three 
to six bacilli of anthrax obtained from the blood of another 
mouse with this disease. Webb, Williams and Barber (1909) 
studied the method of immunizing an animal against a specific 
disease by inoculating the animal with small doses of bacteria, 
beginning with a single cell and then increasing the number. 
In this work the isolation pipette was used so that the cells 
were seen, counted and then inoculated. This was done for 
typhoid, anthrax and tuberculosis. 
Wyssoskowicz (see Adami, 1908, p. 185) claimed that the 
minimal dose required to induce tuberculosis in guinea pigs 
was eight tubercle bacilli; while twenty-four to thirty were 
required for the rabbit. 
A voluminous literature dealing with the effects of measured 
doses of inoculum in animals has developed in the last two 
decades, but these studies were made in connection with work 
in immunity, distribution of parasites, etc., and with no special 
reference to the question under consideration here. 
While I have been unable to find in the literature any ref- 
erence to dosage studies with bacterial parasites of plants, Cobb 
(1904-1905) suggested that the degree of infection of a crop of 
wheat with smut could be determined by counting the number 
of smut spores that could be removed from the seed samples. 
