BIOLOGICAL STUDIES ON INTRACELLULAR BACTERIA. 141 



It will be noticed from the foregoing descriptions that the mor- 

 phological characters of the two species of spirilla are almost 

 identical and if investigation were carried no further, one would 

 doubtless consider the organisms from the two species of cock- 

 roaches as identical. Only in the cultural characters do the dif- 

 ferences become striking and therefore I believe I am justified 

 in considering the microorganisms as two distinct species. Tak- 

 ing Mercier's meager description of the symbiont from Blatclla 

 into consideration we should be inclined to assume that every 

 living species of cockroach harbors a separate species of micro- 

 organism. 



I did not test the pathogenicity of the two cultures on mam- 

 mals. Perhaps this should have been done, since at present a 

 great amount of interest centers on disease transmission by in- 

 sects. Cockroaches are known to carry about and disseminate 

 bacteria mechanically on their feet and in their intestines. Never- 

 theless, investigators interested in this matter might do well also 

 to consider the intracellular organisms. Cockroaches are also in 

 reality living reservoirs of thousands of bacteria enclosed within 

 certain of the hosts' cells. 



3. THE BIOCHEMICAL ACTIVITIES OF THE INTRACELLULAR 



ORGANISMS STUDIED. 



First of all from the sugar tests it is interesting to note that the 

 intracellular organisms do not ferment any of the sugars used. 

 This is very fortunate for the insects. Undoubtedly sugar is 

 present in some form taken in as food and if fermented by zymase 

 secreted by the symbionts might anesthetize the animals with 

 alcohol and CO 2 . 



The inverting enzyme sucrase is not produced by the Parco- 

 blatta symbiont, but the Pcriplaneta organism inverts saccharose 

 to levulose and dextrose. 



Since the organisms are present in the fat body of adults and 

 in the yolk of eggs, it seemed possible that they might have some- 

 thing to do with the metabolism of fat. Experiments with ethyl 

 butyrate, milk fat and other fats failed to demonstrate the exist- 

 ence of lipase. 



The cultural features demonstrated the fact that gelatin was 



