216 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 



as the skin remains whole, nor can it be contracted through either the 

 respiratory or alimentary tracts under normal conditions. It is a 

 blood disease characterized by a breaking down of the erythrocytes^ 

 and like all other diseases of this class can be transmitted only by direct 

 inoculation of blood or other vehicle containing its causative organisms 

 in the infective stage. The only way for such inoculation to take 

 place naturally is through the bites of bloodsucking arthropods. It 

 is further proved that it can not be transmitted to man or other 

 mammals by inoculation of blood taken from a verruga subject while 

 in the fever phase of the disease. 



The almost exhaustive hgematological studies of verruga made dur- 

 ing the past thirty years in Peru and elsewhere have as yet failed to 

 reveal the causative organism of the disease. Barton's a;-bodies, first 

 described by Barton in 19.05, are unquestionably directly related to 

 the fever phase of the disease. They are uniformly absent during 

 the eruptive phase, and uniformly present in the peripheral blood 

 during the fever phase. They seem most likely to be a form of baso- 

 philia caused by a non-infective stage of the pathogenic organism of 

 verruga, which organism is perhaps ultramicroscopic in all its stages 

 and has- thereby successfully eluded observation to date. This causa- 

 tive organism evidently reaches the infective stage only at the end of 

 the fever phase or inception of the eruptive phase, and probably re- 

 mains infective during the persistence of the latter. 



The initial stage of Barton's a:-bodies known by its slender rod-like 

 form, would indicate the beginning of the attack of the pathogenic 

 organism on the erythrocyte. The pyknotic and polymorphous stages 

 would show the successive changes that take place in the erythrocyte 

 during the progress of the attack, which finally results in the destruc- 

 tion of the erythrocytes affected. Cultures made from erythrocytes 

 containing these x-bodies fail to produce verruga on inoculation. The 

 natural deduction is that these bodies are the visible results of a non- 

 infective stage of the organism., which metamorphoses to the infective 

 stage in the subcutaneous tissues thereby giving rise to the eruption. 



The transmission of verruga by bloodsucking arthropods being al- 

 most certainly indicated, the next important point is to know whether 

 or not man is the primary reservoir of infection. This can be quite 

 definitely answered in the negative. The fact that verruga can be 

 contracted in localities uninhabited by man shows that the native 

 fauna constitutes the primary reservoir. This is also unmistakably 

 indicated by the restricted range of the disease. All bloodsucker- 

 transmitted diseases whose primary reservoir lies in the native fauna 

 are originally restricted to the range of that fauna or the portion of it 

 infected. If their transmitters are able to spread outside the original 



