Attenuation of Living Agents of Cyanolophia. 191 



he inoculated in his cultures. In tissue cultures of red bone 

 marrow no multiplication of the virus was observed, but a certain at- 

 tenuation, as proved by the prolongation of the incubation period. 

 Different results were obtained by using white bone marrow. 



Experiment II, 1915. 



Serum C Taken 36 Hours after Inoculation of Virulent Brain B in a 

 Chicken, Shortly before its Death, Was Inoculated in a Tissue 

 Culture of White Bone Marrow and Chicken Plasma. 



Length of Time in Which Virulent Serum B was 

 Cultivated in Tissue Culture at 38 0 C. 



Record No. of 

 Chicken. 



Date of Death. 



Length of 

 Incubation. 



Nov. 30-Dec. 4 



Nov. 30-Dec. 6 



No. 3a 

 No. 4 



Living 

 Living 





Serum C, the Same as Used in Experiment Before, in Red Bone Marrow 



and Plasma. 



Length of Time in which Virulent Serum C 

 was Cultivated in Tissue Culture at 30°C. 



Record No. 

 of Chicken. 



Date of Death. 



Length of 

 Incubation. 



Nov. 30-Dec. 6 



No. 5 



Dec. 9 



72 hours 



This experiment proves that after 4 or 6 days in white bone 

 marrow the virus is attenuated. After inoculation of virus in 

 red bone marrow the animal died. A controlling experiment, 

 in which serum C was used, which was kept 7 days on ice, showed 

 that this serum killed the chicken after 38 hours, the usual time 

 in which this strain of cyanolophia killed the animal. It was 

 perfectly attenuated by the cultivation in white bone marrow, 

 partially by cu'tivation in red bone marrow, and not at all by keeping 

 the serum on ice. 



The inoculation of attenuated serum and white bone marrow 

 protected, to a certain degree, the chicken against a new inocula- 

 tion, as the following experiments prove. 



>»- 



Experiment III, 1915-1916. 



Serum Y Taken 36 Hours after Inoculation of Virulent Brain H in a 

 Chicken, Shortly before its Death, Was Inoculated in a Tissue 

 Culture of White Bone Marrow and Plasma. 



Length of Time in which Virulent Serum y 

 was Cultivated in Tissue Culture at 38 0 C 



Record No. 

 of Chicken. 



Date of Death. 



Length of 

 Incubation. 





No. 3a 



Living 







No. 4 



Living 







No. 6 



Died Jan. 1 



72 hours 



