April, '13] TOWNSEND: VERRUGA AND TICKS 219 



The breaking up of the erythrocytes in verruga is accomplished by 

 an endoglobular activity of the causative organism. The only endo- 

 globular haematozoans known to be transmitted by arthropods are 

 Plasmodium, Piroplasma (Babesia), and Leishmannia. The patho- 

 genic organism of verruga, if not ultramicroscopic, should be either one 

 of these or a closely allied form. Spirochoeta, Trypanosoma and FUaria 

 are exoglobular, and thus excluded. Plasmodium is untenable, since 

 it demands a culicid transmitter which is precluded by the conditions. 

 It is impossible for a mosquito to have such a peculiar range as that 

 indicated by the limiting boundaries of the verruga districts. The 

 limits of these districts do not conform to limiting lines of any known 

 mosquito environment, and the same may be said with regard to the 

 environment of practically all other hexapod bloodsuckers of the region. 

 Leishmannia is excluded as quite certainly transmitted by hexapods 

 only. Piroplasma only remains, and it is especially concerned in tick- 

 borne diseases. All the species of Piroplasma known are transmitted 

 by ixodid ticks, and by these only. Thus, unless the pathogenic organi- 

 ism of verruga be ultramicroscopic throughout all its stages, which it 

 can hardly be, it is probably a form allied to Piroplasma. 



In this connection it is significant that the various species of Piro- 

 plasma known to be transmitted by ticks and to produce piroplasmosis 

 in its various forms have never been unmistakably identified in the 

 bodies of the ticks, though indeterminate bodies have been seen by 

 Koch and other investigators. Is it not possible that Piroplasma or 

 some of its near allies pass an ultramicroscopic stage as sporozoites 

 in the tick? Ricketts found that the pathogenic organism of Rocky 

 Mountain spotted-fever exists in the gut, salivary glands and ovaries 

 of the tick which transmits the disease, and further that it appears to 

 proliferate in the tick. The amount of blood that one of the ticks 

 could hold was found to produce only a mild case of the disease on 

 being artificially injected, while the tick could produce several severe 

 cases from one filling of blood. Inoculations from the salivary glands 

 of the infected ticks produced the disease. Yet the organism itself 

 is not thus far known. Ricketts found that fresh defibrinated blood, 

 washed erythrocytes, and unfiltered serum produced the disease on 

 injection, but filtered serum gave no result. Thus the pathogenic or- 

 ganism of Rocky Mountain spotted-fever appears to be non-filtera- 

 ble, but it is nevertheless apparently ultramicroscopic in its infective 

 stage. Spencer claimed to have found ovoid intracorpuscular bodies 

 showing amoeboid movement, but his results are doubtful. Ricketts 

 found what seemed to be an organism in the blood of infected guinea 

 pigs and monkeys, to a less extent in the blood of infected man, and 

 also in the bodies and eggs of infected ticks. This supposed organism 

 is very likely a parallel to Barton's x-bodies of verruga. 



