Vol. 50 No. 7 
BULLETIN 
OF THE 
TORREY BOTANICAL CLUB 
JULY, 1923 
Studies on plant cancers—IV. The effects of penne: 
various quantities of different dilutions of Bacter 
tumefaciens into the tobacco plant* 
MICHAEL LEVINE 
The early studies of dosage center about the question of the 
transmission of tuberculosis and date back to the period shortly 
before the discovery of tubercle bacilli. Tappeiner (1878-1880) 
was among the first to test the effect of crudely measured 
quantities, such as a teaspoonful and a tablespoonful, of sputum of 
a tubercular patient sprayed into the respiratory tract of a dog. 
In 1890, Gebhardt, under favorable and aseptic conditions, studied 
the effect of inhalations of tubercle bacilli and also intraperitoneal 
and subcutaneous injections of the same organism into the 
guinea pig. He used the expressed milk of the udder of tuber- 
cular cows, the sputum of phthisis patients, and pure cultures of 
the bacillus grown on beef-peptone-glycerine. With the pure 
cultures he used 5 cmm. to 2 cc. sterile water. This suspension 
was diluted 1 : 400 and used as a mother liquor. Intraperi- 
toneal injection of a dilution of the mother liquor in a proportion 
of 1 : 500 gave tuberculosis. Very dilute suspensions induced 
tuberculosis by inhalation and subcutaneous injections, Preyss 
(1891) made a more determined effort to establish the quantity 
of tubercle bacilli necessary to cause tuberculosis. He found 
that a droplet 1/1000 mg. of sputum which contains forty tubercle 
bacilli was sufficient to induce tuberculosis in the guinea pig. 
He made no actual count of this number but estimated it on the 
basis of 1 mg. moist culture of tubercle bacilli, which he claimed 
contained thirty-five million organisms. 
* From the Cancer Division, Montefiore Hospital, Dr. Isaac Levin, Chief. 
[The BuLLETIN for June (50: 197-230. pl. 9-12) was issued July 6, 1923.1 
231 
