No. 6. DEPARTMENT OF AGRICULTURE. 149 



tioii of tlu' bull with a (luautily of virulent culture nearly twice as 

 great as was necessary when similarly administered to kill an un- 

 lifotected heifer did not, so long as he was permitted to live, appre- 

 ciably disturb his gc4»eral health. The humau sputum culture M 

 used for these inoculations was obtained by Dr. Ravenel from the 

 sputum of a consumptive woman in September, 181)1). As a further 

 indicatiou of its degree of virulence^ it may be noted that two guinea- 

 pigs were inoculated, subcutaneously, December 18, 1901, each with 1 

 c. c. of a staiulard sus[)cnsion of this culture. One guinea-pig died 

 March 8 and the otlier March 20, of geiieralized tuberculosis. Two 

 rabbits were also inoculated December IG, 1901, each with 2 c. c. of 

 the same suspension. Both died suddenly in June, one on the 3d 

 and the other on the 10th, from having been given improi»er food. 

 Both were free from all evidence of tuberculosis and showed no al- 

 teration excepting dili'use redness of the intestines. 



These experiments tend strongly to show that cattle may be re- 

 fractory to enormous quantities of tubercle bacilli from human spu- 

 tum when injected into the blood beneath the skin, into the peritoneal 

 cavity or into the lungs; and the result upon one of the animals (the 

 bull) indicates that after such treatment the resistance to virulent 

 culture of bovine origin may be increased. 



An experiment was inaugurated in March of this year, to again, 

 and more definitely, test the immunizing value of repeated intra- 

 venous inoculations of cultures of sputum tubercle bacilli not viru- 

 lent for cattle. For tlH> juirpose of this experiment four young cattle 

 were used, as follows: A black and white bull, sixteen months old 

 (460GG); a red heifer, twelve months old (4r)()()8); a red heifer, fifteen 

 months old (450G7), and a red heifer, eleven months old (45071). All 

 were tested with tuberculin and were })roven to be free from tuber- 

 culosis. They were divided into two groups of two each as nearly 

 equal as possible in respect to age, size, and general condition. The 

 animals of one group were inoculated intravenously seven times be- 

 tween March 24th, and June 2, with gradually increasing quantities 

 of from 10 c. c. to 2.5 c. c. of a standard suspension of a culture of 

 sputum tubercle bacilli. In all, 125 c. c. of this suspension were ad- 

 ministered, representing about 0.1 G gramme of tubercle bacilli. 



Each of the four animals in this experiment — the two that had 

 been vaccinated (450G(! and 450G8) and the two kept as controls (450G7 

 and 45071) — was inoculated July 29th by injecting into the trachea 

 10 c. c. of a standard suspension of bovine tubercle bacilli (culture H) 

 known to be virulent for cattle. The intratracheal method of inocu- 

 lation was used, because it furnished a means of conveying tubercle 

 bacilli into the organs most frequently infected in nature and in a 

 manner unattended by disturbance of function or with material 



