Pellagra 247 



article of diet, and that its spread was not pari passu with that of the 

 use of corn. Cases were found in which the patients had apparently 

 never used corn, 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, in patients 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 



