240 



STRONG AND TEAGUE. 



infection by inhalation with a pneumonic strain which had been passed 

 through a series of gninea pigs. The growth from 3 agar-slant-cultures 

 was suspended in about 40 cubic centimeters of normal saline solution and 

 all of this suspension was used for the spraying. Only three or four 

 vaccinated monkeys with the same number of controls were placed in a 

 cage at a time during the spraying. They were then, of course, placed 

 in separate cages. The result of the experiment was as follows: 



Series IV. — Infection 



by inhalation. 



Vaccinated monkeys, a 



Normal monkeys. ^ 



No. 5704 survived. 



No. 



5771 survived. 



No. 5706 died in 6 days. 



No. 



5772 died in 5 days. 



No. 5707 survived. 



No. 



5773 died in 5 days. 



No. 5708 died in 4 days. 



No. 



5774 died in 6 days. 



No. 5709 died in 6 days. 



No. 



5775 survived. 



No. 5710 died in 5 days. 



No. 



5776 died in 5 days. 



No. 5711 died in 5 days. 



No. 



5777 died in 5 days. 



No. 5712 survived. 



No. 



5778 died in 6 days. 



No. 5713 died in 7 days. 



No. 



5779 died in 6 days. 



No. 5714 died in 8 days. 



No. 



5780 died in 5 days. 



No. 5715 survived. 



No. 



6781 died in 5 days. 



No. 5716 died in 6 days. 



No. 



5782 died in 5 days. 



No. 5717 died in 5 days. 



No. 



5783 died in 8 days. 



No. 5718 died in 6 days. 



No. 



5784 survived. 



No. 5719 died in 8 days. 



No. 



5785 died in 6 days. 



No. 5720 survived. 



No. 



5786 died in 4 days. 



No. 5721 survived. 



No. 



5787 died in 4 days. 



No. 5722 survived. 



No. 



5788 died in 5 days. 



No. 5724 survived. 



No. 



5789 died in 4 days. 



No. 5725 died in 6 days. 



No. 



5790 died in 5 days. 



No. 5726 died in 6 days. 



No. 



5791 survived. 



No. 5727 survived. 



No. 



5792 died in 5 days. 



^ Total : Survived, 9 ; died, 13. 

 b Total : Survived, 4 ; died, 18. 



Nine, or 40.5 per cent, of the vaccinated monkeys survived, 

 while 4, or 18.1 per cent, of the unvaccinated control ones also 

 survived. In this experiment, evidently the method of produc- 

 ing the infection was not satisfactory, since four of the control 

 unvaccinated monkeys did not develop plague infection. The 

 results obtained in Series IV, therefore, do not give as valuable 

 information as do the results obtained in Series III and V. 



EXPERIMENT NO. 5. 



On October 18, 1911, twenty-one monkeys were each vaccinated subcuta- 

 neously with one 48-hour agar-slant-culture of living avirulent plague 

 bacilli. On November 2, these animals and 21 control unvaccinated ones 

 were exposed to infection by inhalation in the same manner as in the 

 preceding experiments. The result may be tabulated as follows: 



