1918] Glaser — On the Existence of Immunity Principles in Insects 45 



Experiments. 



(1) 2 drops' 9 femuT-ruhrum immune blood + 1 c.c. bouillon + 1 loop of B. poncei. 



(2) 2 drops 9 femur-rubrum immune blood + 1 c.c. bouillon + 1 loop of B. poncei. 



(3) 2 drops (^ femur-rubrum immune blood + 1 c.c. bouillon + 1 loop of B. poncei. 



Checks. 



(1) 2 drops bouillon + 1 c.c. bouillon + 1 loop of B. ponce j. 



(2) 2 drops 9 /eTOwr-ruftruTO normal blood + 1 c.c. bouillon + 1 loop of B. poncei. 



(3) 2 drops cf femur-rubrum normal blood + 1 c.c. bouUlon + 1 loop of B. poncei. 



The six test tubes were incubated for 24 hours at 35° C. At the 

 end of that period neutral potato agar plates were poured from the 

 six cultures using the customary one, two, and three dilution 

 method. Each experiment and each check was represented by 

 three plates making eighteen plates altogether. They were in- 

 cubated for three days at 35° C. after which a count was made of 

 the developed colonies. The colonies on the six first dilution 

 plates (experiments and checks) were too numerous and confluent 

 for counting. Those on the six second dilution plates were also 

 extremely numerous. At a glance one could tell that the colonies 

 on the check plates were more numerous than on the experimental 

 plates. By taking counts of sections of all the plates I arrived at 

 the conclusion that the ratio of check to experimental colonies was 

 about 10: 1. 



With the six third dilution plates I was able to make actual 

 colony counts for the three experiments and three checks. 



Number of Colonies on Third Dilution Plates. 



Checks. Experiments. 



(1) 7 



(2) 4 



(3) 6 



As can be seen from the foregoing table Checks 1, 2, and 3 gave 

 7, 4, and 6 colonies respectively, whereas nothing at all was ob- 

 tained on the three third dilution experimental plates. 



These experiments taken in conjunction with the other results 

 I have presented show that it is possible to bring about the forma- 

 tion of bacteriacidal properties in some insects. From my tissue 

 culture work discussed under phagocytosis, I have shown that 

 normal insect blood is somewhat antagonistic towards bacteria, 



1 Two drops equals Ve of a cubic centimeter. This is the maximum amount of blood which 

 one can obtain from one animal at a time. 



