The impenetrable chaparrals in the extensive plains between the Nueces and the Rio Grande, formed of mosquito-shrubs, six to seven feet high, entwined with lianes; the palmetto-fields on the shores of the Sabine, Natchez, and other rivers of Texas, formed of rush and dwarf palms; the low acacia bush of Australia Felix, and lastly the wide jungles traversed by the elephants and tigers in the East Indies, and formed of bamboo and other lofty grasses, are all peculiarly characterized formations of bush, which often not attaining the height of a man, or but little exceeding it, do not all betray at the first glance the frequently insuperable obstacle they oppose to the intruder, and even after man has settled in the neighborhood can only be traversed by paths which the wild animals have made. With a kind of feeling of disappointed expectation rides the traveler in the prairies of the West, anything but refreshing appears the monotonous surface uniformly overgrown with high grass, the line of the horizon unbroken even by the smallest elevation. He rides and rides, but ever boundless space expands before his eyes, in the same uniformity, in the same calm simplicity. [Illustration: Bacteria and Vegetable Germs 3, Pneumonia; 5, Anthrax; 7, Diphtheria; 8, Tuberculosis; 9, Leprosy; 10, Tetanus; 11, Influenza; 12, Typhus; 14, Cholera] Situated under similar latitudes and climatal conditions, the pampas of Buenos Ayres have a character similar to that of the North American prairies, only man by his influence on nature has here and there impressed a peculiar stamp. The thistle and artichoke, coming with the Europeans, have quickly made themselves masters of the free soil, and with incredible rapidity overspread districts of many square miles with their spiny vegetation, which has here developed in a luxuriance unknown in Europe. These thistle-wastes have become a terrible nuisance, themselves robbers, depriving better plants of the soil, inaccessible hiding-places for the great thievish, sanguinary cats, and the still more dangerous human bandits, the thorny weed of semi-civilization.