Pellagra 
247 
article of diet, and that its spread was not pari passu with that of the 
use of com. Cases were found in which the patients had apparently 
never used com, though that is obviously difficult to establish. He 
showed that preventive measures based on the theory had been a 
failure. Finally, he believed that the recurrence of symptoms of 
the disease for successive springs, inpatients who abstained absolutely 
from the use of corn, militated against the theory. 
On the other hand, Sambon believed that the periodicity of the 
symptoms, peculiarities of distribution and seasonal incidence, and 
analogies of the symptoms to those of other parasitic diseases indi- 
145. Pellagrous eruption on the hand. After Watson. 
cated that pellagra was of protozoal origin, and that it was insect- 
borne. 
The insect carriers, he believed to be one or more species of 
Simuliidse, or black-flies. In support of this he stated that Simulium 
appears to effect the same topographical conditions as pellagra, 
that in its imago stage it seems to present the same seasonal incidence, 
that it has a wide geographical distribution which seems to cover 
that of pellagra, and that species of the genus are known to cause 
severe epizootics. Concluding from his studies in Italy, that pel¬ 
lagra was limited almost wholly to agricultural laborers, he pointed 
out that the Simulium flies are found only in rural districts, and as a 
rule do not enter towns, villages, or houses. 
When Sambon’s detailed report was published in 1910, his theory 
was seized upon everywhere by workers who were anxious to test it 
