1918] Glaser—On the Existence of Immunity Principles in Insects Al 
the preparations were studied and I was astonished to find that 
they were surprisingly free from Bacillus poncei. Six of the smears 
showed no microédrganisms whatever, the remaining ones showed a 
few bacilli 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 4 hour; two after 
1 hour; two after 2 hours and four after 24 hours. The bacteria 
were found in one case examined after 3 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 view. The blood of a certain number of the inoculated 
animals managed to rid itself of B. poncet and, moreover, this rid- 
dance was not accomplished by hungry amebocytes 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 
known methods used by Harrison, Carrel, etc. for the cultivation 
of embryoni¢ 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 Growth of Insect Blood Cellsin Vitro.”” Psycur, Vol. XXIV, No. 1, 1917. 
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