CLIMA TOLOG Y—^TIOLOG Y 



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acquired at an elevation below 2,800 feet or above 9,000 feet, nor 

 does it originate in the main valleys. 



One striking peculiarity common to all the places is that they are 

 in narrow valleys along tributaries of rivers. The principal infected 

 areas are Tablachaca, Pallusca, Corongo, Pacatqui, and Ninabamba, 

 in Pallusca; Huaylas and Caraz, in Huaylas; Yautan, Pariacoto, 

 Rurasca, Nanca, Jangas, Pongor, Anta, and another district on a 

 branch of the River Huarmey, in Huaraz; Cochas, Huaylillas, and 

 Cajatambo, in Cajatambo. 



In the department of Lima there are six provinces, of which 

 Chancay, Canta, Huarochiri, and Yauyos possess endemic areas, 

 which vary in height from 900 to 2,030 metres. In Chancay 

 there is Huaycho; in Canta, Acos, Viscas, Yasu, Magdalena, and 

 Yangas; in Huarochiri, Santa Eulalia, Palle, San Geronimo, San 

 Pedro de Casta, Surco, Cocachacra, Santa Ana, and Sisicaya; and 

 in Yauyos, Omas. 



The best-known area is that which lies along the railway from 

 Lima to Oroya, which begins a little below the division of the River 

 Rimac into the rivers Santa Eulalia and Cocachacra, along both of 

 which the disease is endemic for some distance, including Santa 

 Eulalia, San Geronimo, Cupichi, San Pedro de Casta, San Pedro 

 de Mama, Santa Ana, Corcona Cocachacra, San Bartolome (where 

 the stream which runs into the Cocachacra River is called the 

 Aqua de Verrugas, because the people believed the disease came 

 from drinking the water), Cuesta Blanca, and Surco. 



Here again, as in the department of Ancachs, the disease is 

 restricted to certain deep, narrow valleys, locally known as 

 ' quebradas,' along which streams flow, and which are some 28 to 

 60 kilometres distant from the littoral, where the disease never 

 occurs. A very important epidemiological point is that the disease 

 only occurs in the summer when the rivers are in flood, and when all 

 sorts of insects abound. Monge points out that earthquakes are 

 correlated with small epidemics, probably because the disturbed popu- 

 lation becomes more exposed to the infection, whatever that maybe. 



-ffitiology. — ^The causation of verruga peruviana is unknown. 

 Popularly the disease is believed to be conveyed by the drinking- 

 water, which, however, has long been discredited. In 1875 Pan- 

 corvo, taking into consideration the well-known fact that the persons 

 who mostly suffer are people who work in the fields or disturb earth, 

 suggested that it was an intoxication due to sulphuretted hydrogen 

 liberated from the earth, a view which never received any marked 

 support. Odriozola and Tamayo have failed to find any bacteria 

 in people suffering from the eruption of Peruvian wart. It is said 

 to occur in animals, especially quadrupeds, and not to be con- 

 tagious. Chastang believes that some germ is inoculated by the 

 thorns of Cactus opuntia. Long ago Raymondi suggested that 

 verruga would, like rabies and syphilis, be found some day to be 

 due to a definite virus. Translating Raymondi's views into modern 

 thought, it would mean that the three diseases would be found to be 



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