16 E. V. COWDRY. 



noticeable modifications except a slight reduction in height. Al- 

 though very careful search was made, none of the microorganisms 

 were detected in the ovaries. Another point of similarity to 

 Rlckettsia was that the microorganisms did not reveal their pres- 

 ence by causing noticeable sickness in their insect-hosts. 



Bacteria of larger size and staining blue by Giemsa's method 

 were occasionally observed in small numbers within the body cav- 

 ities of the same insects ; but not in the intestinal lumina, or within 

 the Malpighian tubules. Some of these bacteria are shown in the 

 lower part of Fig. 2. 



The alimentary tract, though well developed, was never dis- 

 tended with food but contained a small amount of a coagulum 

 which might well have been produced by the action of enzymes 

 and fixatives upon plant juices accepting the evidence of Ouain- 

 tance, 2 Snodgrass, 3 and others that the insects take food of this 

 kind. Hargitt, 4 on the other hand, is of the opinion that the in- 

 sects seldom if ever feed in the adult state. If substantiated, 

 Hargitt's view will narrow down a search for the port of entry of 

 the parasites. 



The term " Rickettsla " has been applied to an ill-defined group 

 of microorganisms which are difficult to classify with certainty ow- 

 ing chiefly to their resistance to ordinary methods of artificial cul- 

 tivation. It was first used by da Rocha Lima, 5 in honor of Doctor 

 H. T. Ricketts, who died while investigating typhus fever, to des- 

 ignate certain peculiar microorganisms which he found in coopera- 

 tion with Doctor R. M. Wilder. Since that time the word has 

 gradually become generic in its scope and is now generally con- 

 ceded to include also the parasite of Rocky Mountain spotted 

 fever, certain organisms held to be responsible for trench fever 

 and Japanese River sickness, as well as many which are not 

 known to be pathogenic for man. About 25 different varieties of 

 Rickettsia have thus far been reported. According to \Yol1 >;ich. 



* 



2 Quaintance. A. L., Bull. No. 87, Maryland Agr. Exp. Sta., 1902. 

 8 Snodgrass, R. E., Smithsonian Report for 1919, published 1921, 381. 

 Hargitt, C. W., BIOL. BULL., 1923, XLV., 200. 

 o da Rocha Lima, H., Bcrl. klin. IVchnschr., 1916, I. III., 567. 

 8 Ricketts, H. T., and Wilder, R. M., J. Am. Mcd. Assn., 1910, I. IV., 1304, 

 1373. 



