1918] Glaser — On the Existence of Immunity Principles in Insects 41 



the preparations were studied and I was astonished to find that 

 they were surprisingly free from Bacillus yoncei. Six of the smears 

 showed no microorganisms whatever, the remaining ones showed a 

 few bacilH scattered about here and there outside of the blood cells. 

 On examining each smear carefully by studying ten fields with the 

 oil immersion lens, I found only one blood corpuscle with B. 

 poncei embedded in its cytoplasm. If the grasshoppers had been 

 permitted to live, I feel sure that only the four revealing any 

 bacteria in the blood would have finally died of the disease. The 

 remaining six would have lived till they succumbed to natural 

 causes. Two animals were examined after | hour; two after 

 1 hour; two after 2 hours and four after 24 hours. The bacteria 

 were found in one case examined after ^ hour, in two examined 

 after 2 hours and in one examined after 24 hours. This experiment 

 was repeated with similar results. 



In many of the inoculation experiments with B. poncei from one- 

 fourth to one-half of the animals did not die and I then assumed 

 that the blood acted antagonistically towards the introduced bac- 

 teria. The blood tests cited above seemed to be evidence in favor 

 of this ^-iew. The blood of a certain number of the inoculated 

 animals managed to rid itself of B. poncei and, moreover, this rid- 

 dance was not accomplished by hungry amaebocytes as the text- 

 books would have us believe. If the grasshopper blood cells had 

 phagocytised large numbers of the bacteria I surely would have 

 noticed this in the stained smears. In some cases the blood, how- 

 ever, acted antagonistically towards the bacteria and I will later 

 show more clearly that the antagonistic substances are extracellular 

 and therefore in the blood plasma or serum. 



I thought that the tissue culture method might offer some in- 

 teresting possibilities in studying, in vitro, the behavior of insect 

 blood cells towards bacteria. The method for preparing such 

 cultures is very simple and does not differ materially from the well 

 kno^Ti methods used by Harrison, Carrel, etc. for the cultivation 

 of embryonic mammalian tissue. I shall not describe a method 

 familiar to all biologists.^ 



The results of the following four experiments may be considered 

 characteristic for a large series performed with both grasshopper 



1 Those interested in the cultivation of insect blood cells may be referred to R. W. Glaser: 

 "The Grow-th of Insect Blood Cells in Vitro." Psyche, Vol. XXIV, No. 1, 1917. 



