BACTERIOLOGY OF CITY STREETS.

Evening Star, Issue 11824, 2 March 1903, Page 3

BACTERIOLOGY OF CITY STREETS.

The Commissioner of Street-cleaning of New York City, Dr Woodbury, has made a new departure in his work by causing a bacteriological examination to be made of the streets in various sections of the city. The results are interesting in the highest degree. The following is a description of the tests and the deduction made from them:—“At various points selected to give strong contrasts between typical conditions, plates coated with a medium prepared in the laboratory of Cornell University Medical College were exposed on different days corresponding as to weather. These plates were each exposed for half an hour at the kerb level and 6ft above the kerb. The micro-organisms collected by them were subsequently transferred to a medium favorable for their growth, and kept at a uniform temperature, and when the germ colonies had developed they were magnified 700 diameters and photographed. From the standpoint of the number of colonies alone—that is, dealing with dirt in abroad sense—there are several points that are plainly demonstrated, and others that may require exposures of plates over long periods to warrant conclusions. The germ colonies chiefly in evidence in ■ the photoenlargements thus far made are those characteristic of organic decomposition. In the aggregate they are probably not pathogenic. There is every warrant, however, for believing that they carry large numbers of disease germs. The next step will be to continue the cultures further, and by microscopic study segregate and count certain _ bacilli recognised as those of diphtheria, tuberculosis, and other contagious diseases.” In order to eliminate chance results and to make the tests as uniform as possible, exposures, we are told, were made on the same side of the street and at the centre of the block, care being taken to select localities that were similar not only in height of buildings and in kind of pavement, but also with reference to the work going on in the vicinity. The same care was exercised also in other respects, so that the different series of observations may properly be compared. To quote further:—“ Among the points established by the results thus far reached is the fact that air taken at or near the kerb level is much mere heavily laden with what Professor Ewing has humorously described as ‘ ( the rich bacterial flora of these localities’ titan that taken at a level of 6ft or more above the sidewalk. This is not surprising, but it is worth noting, as possibly accounting for the greater susceptibility of infants than of adults to diseases of zymotic origin. Obviously, unclean streets are vary unsafe playgrounds for small children. Another safe conclusion is that the character of the street traffic determines in great degree the . distribution of bacteria in air currents. The vibrations and disturbances caused by the passage of a slow-moving, heavy truck have the effect of loosening the dust and the street dirt in the interstices of the pavement and on the surface. This is more or less true of all traffic, but especially so of heavy carting. Light and rapid traffic create air currents which pick up the dust an< L (^rt the air. Rapid and heavy traffic, such as street cars, acts 1 both as a loosener and a distributor of the dirt. This is especially true of electric cars, which hug the surface and make strong currents of air... The surface of the streets, therefore, should not only be as clean as .possible, but* the dust should be so treated

.as. to resist'the effort of traffic to disseminate it. “ Still ‘another conclusion deduced from comparisons of results in different localities is that adequate but hot too copious street flushing is the method which most effectually minimised the organisms carried by the air. The general conclusion' that .dean asphalt streets in orderly residential neighborhoods are traversed by purer air than that to be gathered among the pushcarts and above the filth-laden pavements of the crowded tenement districts is too obvious to need discussion. If proof were needed, however, it is found in a count of bacterial colonies on plates given exposures in clean and unclean neighborhoods. When it is found, for example, that a plate exposed for half an hour in a dean, orderly uptown residential street with a well-swept asphalt ‘pavement shows five isolated pinhead colonies after an enlargement of 700 diameters, while one exposed for the,same length of time and under identical conditions of hour and weather in a lower East Side street lined with crowded tenements, from the windows of which tons of putres--816 daa y thrown, shows nearly 10,000 confluent colonies, some as laree as the print of a man’s thumb, covering the whole microscopic field, the difference in the nealthfulness of the two neighborhoods is easily accounted for. Plates of this kind are useful object-lessons for those who regard municipal cleanliness as a fad, tolerable if not too costly. If they show anything. it is that clean streets are worth all . ey cost, and that negligence in their care is criminal eiflavagance.”