bacilli from blood which had necessarily passed through the pul- 

 monary circulation, and by the presence of bacilli in blood which 

 needed to go only from a peripheral artery to the corresponding 

 peripheral vein. Possibly this quality of the lung capillaries may be 

 one of the causes of the great frequency of pulmonary involvement 

 when tubercle bacilli have entered the body at points distant from 

 the lungs. 



It will be noticed that inoculation produced in a healthy young 

 steer a rapid and fatal miliary tuberculosis, while in Cows 3 and 7 

 not more than an aggravation of the existing extensive chronic 

 tuberculosis was brought about. It would appear that long-standing 

 chronic tuberculosis produced a ,much higher power of resistance 

 against newly introduced infection than did the intravenous injec- 

 tion of attenuated cultures. That cattle affected with chronic tuber- 

 culosis should be somewhat resistant to acute tuberculosis from 

 inoculation would be expected; but the great resistance shown by 

 Nos. 3 and 7 to overpowering introductions of virulent bovine bacilli 

 into the blood stream is interesting and suggestive. 



The work on tubercle bacilli in the blood was done in conjunction 

 with Wilbur A. Sawyer, M. D., physician at the University of Cali- 

 fornia Infirmary, Berkeley. 



Dr. Sawyer and I are indebted to Archibald R. Ward, B. S. A., 

 D. V. M., Assistant Professor of Bacteriology in the University of 

 California ; to Miss Margaret Henderson, B. S., Instructor in Bacteri- 

 ology in the University of California ; to David N. Morgan, B. S., and 

 to Ned D. Baker, B. S., for valuable advice and assistance. 



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