22 NATURAL REGIONS OF ARGENTINA 



belt of selective breeding, which slants across the 

 plain of the Pampas from the Sierra de Cordoba to the 

 Parana. The more or less degenerate cattle of the 

 natives had spread over the whole of the South 

 American continent, except the tropical forests, since 

 the seventeenth century, adapting themselves easily 

 to very different climatic conditions, from the Venezue- 

 lan llanos to the sertao of Bahia and the plains of 

 Argentina. But pedigree animals, more valuable 

 and more delicate, introduced on to the Pampas fifty 

 years ago, are not able to resist the malady caused by 

 a parasite called the garrapate. Hence the southern 

 limit of the garrapate suddenly became a most im- 

 portant element in the economic life of the Republic. 

 It would lose its importance if we discovered a serum 

 that would give the animals immunity against Texas 

 fever. 



The range ot one and the same cause varies infinitely 

 with the circumstances. The limit of the prairie, as 

 of the scrub [monte) which surrounds it on every side, 

 and keeps it at a distance of 320 to 440 miles from 

 Buenos Aires, had no decisive influence on primitive 

 colonization. Whether covered with grasses or brush- 

 wood, the plain is equally suitable for extensive breed- 

 ing. The ranches are the same on both sides of 

 the border. At the end of the nineteenth century, 

 however, when the area of cultivation increased, the 

 prairie was at once found to be superior. The labour 

 required for clearing the brushwood before the plough 

 can work is enough to divert from it, at least for some 

 time, the stream of agricultural colonization. While 

 the population of the monte, wood-cutters and breeders, 

 are indigenous, the prairie has absorbed the immigrants 

 from Europe, and the border of the scrub has become 

 in many places an ethnographical frontier.^ 



The changes which man has made in the floral land- 



' See E. A. S. Delachaux, " Las regiones fisicas de la Republica 

 Argentina," Rev. Museo Plata, xv, 1908, pp. 102-131, 



