more prominent rods will be pressed down, showing their peculiar shape. Another source of deception is the fact that these bacteria are apt to move about with a gyratory motion, with extremity directed towards the observer. Watching such a particle carefully, it may sometimes be seen to turn and expose its side, and then we may see that it is nothing but the ordinary rod-bacterium. When we have to do with other particles, then indeed it is well to give.diagnostic points by which we may distinguish them from ordinary granular matter, such as fragments of tissue, minute oil particles, pigmentary matter, etc. I feel confident, however, from repeated examinations, that no particles have been described by Oertel as micrococci, that can be positively shown to be present in diphtheria alone. On the contrary, both Dr. Curtis and myself have repeatedly examined the accumulations in our own mouths, and have there seen the forms which are described as belonging to diphtheria.

And yet diphtheritic membrane is very poisonous, and fatal when inoculated in the muscles of rabbits, as I have had repeated opportunities of observing. I may here state that Oertel's descriptions are the most elaborate and, perhaps, the most clearly given of any writer's on the experimental pathology of diphtheria; as far, however, as my experience has gone, it has in most instances failed to verify them. In inoculating the corneæ of rabbits, in a number of instances, no lesion followed, beyond an ordinary keratitis, and none of the rabbits died; in fact they all recovered quickly. The fresh diphtheritic membrane, when inoculated, was very fatal, the tendency to death being extremely common about the end of the second day. Of 27 rabbits inoculated with the solid membrane, or an aqueous infusion of it, 20 died, and 12 at about the end of the second day, or between the second and third.

Now the membrane when thoroughly boiled, was equally fatal in two cases, and yet boiling is said by most excellent authorities to destroy bacteria. In fact, this is a matter of general belief. Furthermore, bacteria were shown to decrease rather than increase, when introduced into the system, so that certainly after two or three weeks they had either become distorted, so as to be hardly recognized, or they had altogether disappeared. When very strong solutions of salicylic acid, combined with phosphate of sodium as a solvent, were made up into a paste with diphtheritic membrane, and inoculated in the thighs of rabbits, they produced a fatal disease, though the lesions were not as extensive as when diphtheritic membrane alone was used; and yet, in my experience, salicylic acid in the proportion of has, as before mentioned, prevented the development of bacteria for from twelve to twenty-five days.

I believe that I have now given a tolerably fair account of the most prominent views entertained on the matter of disease-germs, and think that I am warranted in submitting the following conclusions with regard to the present status of the question :--

I. That, as far as inquiry has been made as to the nature of the active principles in infective diseases, it is probable that in a certain number the matter is particulate, or molecular in form.

II. That in regard to the causes of septicemia, pyæmia, puerperal fever, erysipelas, and hospital gangrene, and those of cholera, vaccinedisease, the carbuncular diseases of men and animals, typhoid and relapsing fevers, and diphtheria, there is not satisfactory proof that they are necessarily connected with minute vegetable organisms.

III. That the real nature of these causes is still uncertain.

VITAL STATISTICS OF BUENOS AYRES.

BY

G. RAWSON, M.D.,

OF BUENOS AYRES.

A BRIEF review of the vital statistics of Buenos Ayres may perhaps awaken some interest in the International Medical Congress now assembled in Philadelphia, not only as adding to the data accumulated from day to day as elements of Sanitary Science, but as presenting circumstances peculiar to that Argentine city itself.

Buenos Ayres, next to Rio de Janeiro the most populous city in South America, has grown with extreme rapidity, having tripled its population within the last twenty-five years, mainly owing to the vast tide of emigration from European shores. But, even in the event of a diminution of the influx of immigrants, and a corresponding reduction of the rate of increase, it is almost certain that Buenos Ayres will, at the close of the present century, have upward of half a million inhabitants. Situated in latitude 35° south, with a genial climate, it is exempt from the extremes of temperature so common in other localities; and, were it not for the modifying influences exercised upon its sanitary condition by the increase of population, and by the circumstances usually attending that increase when not overruled by strict observance of the admonitions of science-it would be as healthy a city as its name (good air) would seem to imply.

But the death-rate in Buenos Ayres attains proportions by no means. satisfactory; and the recent epidemics, particularly the yellow-fever scourge of 1871, show that much has to be done before the city can regain that salubrity reasonably to be expected from its situation and soil, and from the prevailing winds and other climatic conditions with which it is favored by Nature. Epidemics are warnings to mankind— warnings all the louder in proportion to the severity of the visitation; and Buenos Ayres has learned from her recent sufferings the lesson to be desired. Works, both above and beneath the surface, are now in prosecution for the sanitary improvement of the city, by means of a system of drainage and underground disinfection which will cost twenty millions of dollars (eight millions have already been expended), and which, when completed, will be one of the most efficient in the world.

Besides, the population of the city is, to a great extent, composed of foreign elements permanently incorporated therein and constantly increasing. In this respect Buenos Ayres bears a striking analogy to many cities in the United States, and, like these, presents a series of phenomena peculiar to this species of social evolution, as revealed in its vital statistics. The analogy here referred to I shall endeavor to point out in the course of the present essay.

Population of Buenos Ayres.-It is necessary, first of all, to determine the population of Buenos Ayres, and its component elements; but the accurate accomplishment of this is difficult, owing to the long intervals between the censuses, and the rapid increase of the number of inhabi

tants. The mode of development in cities of the New World is in general so irregular that, in measuring their growth, it will not suffice merely to determine the difference between the numbers of births and deaths. The increase resulting from that tardy process is insignificant when compared with that derived from immigration, and with that which is due to the irresistible attraction which populous centres exercise at all times upon neighboring towns. This species of attraction is, from causes peculiar to the Argentine Republic, more powerful in Buenos Ayres than in other American cities of similar growth. In 1871, for example, the number of victims of the disastrous yellow-fever epidemic exceeded that of the births in the same year by 13,206: but the equilibrium of the population was more than re-established by the influx of emigrants from Europe, and from the surrounding provinces and republies. By comparing the total number of births during the period from 1858 to 1872 with the total number of deaths during the same period, including, of course, the victims of the cholera of 1867 and 1868 and those of the yellow fever of 1871, we observe an excess in the deaths, of 1778. Hence, if Buenos Ayres had depended solely upon its own resources for its growth, its population, instead of increasing, would have diminished. But the ravages of this frightful mortality were more than compensated for by immigration, and the remarkable growth of the city pursued its course without any apparent interruption.

The progress becomes more and more marked, dating from 1852. In the absence of official data, it is scarcely possible to estimate the population of Buenos Ayres in that year, which was marked by a political event of transcendent importance-the downfall of the dictatorship by which the nation had been oppressed and depopulated for the space of twenty years. Numerous emigrants returning to their homes after a prolonged proscription; the establishment of liberty, political and civil; the opening the navigable rivers to the vessels of all nations; the discovery of riches susceptible of being developed advantageously in the Argentine Republic by the hand of man; and the facilities offered by both the government and the people to foreigners desiring to take up their residence there, induced a stream of European immigrants, which continued uninterruptedly for a number of years. Dating from the beginning of the influx of foreigners, the rapid growth of the population became evident, and about that time the greatest increase took place. Nevertheless, no census of the city was taken until 1855, nor was a second effected until 1869, the year of the general census of the republic. According to the terms of the constitution, the general census will in future be taken every ten years.

The two censuses referred to are, therefore, the only available data on which to base my computations; those for other years must, of necessity, be only approximate. In the census of 1855, the total population of the city was set down at 91,548, and in the general census of 1869, at 177,787. Hence, the mean annual rate of increase during the period embraced between these two extremes would be 4.8 per cent., always supposing the progression to have been uniform. Now, by applying the same system of reckoning to the previous years, that is to say, from 1852, and to the successive years down to 1875, the population of Buenos Ayres would be as in the annexed table in the years therein expressed :—

On reviewing the foregoing statement of the increase of the population, two objections are apparent, and I must now endeavor to explain them. They are: first, the epidemic of 1871, which would appear to have checked for the time being the numerical advancement of the population; and, second, the perceptibly decreased immigration in the last two years, 1874 and 1875.

Buenos Ayres is not only the chief port, but also, by reason of its position, the natural centre of all movement in the republic. It is the point of disembarkment for the immigrant on his arrival, and of re-embarkment for those who return to Europe. Passengers, whether immigrants or not, coming from Montevideo, likewise land at Buenos Ayres; and there they go on shipboard again when leaving to go back. There, too, is the rendezvous of all craft navigating the tributary streams of the Rio de la Plata. Hence, the movement of passengers throughout the year may at all times be readily ascertained, and the balance to the credit or debit of Buenos Ayres accurately determined by comparison of the arrivals and departures. The communications by land are extremely limited, and confined to the rural districts of Buenos Ayres and the neighboring provinces. It is generally admitted that more than twothirds of all immigrants to the republic, come whence they may, remain in Buenos Ayres city, the remainder being distributed through the surrounding country. The following table shows the movement of passengers for the port of Buenos Ayres in the years 1864-72:

As seen in the foregoing table, in 1870, the year immediately following the general census, the balance in favor of the population reached the highest point so far known, as far as the arrival and departure of passengers were concerned. That year was an auspicious one for the city. Immediately after the termination of the Paraguayan war, a vast accumulation of capital was effected, credit facilities were opened up, encouragement was offered to such as desired to embark in new industrial enterprises, and important public works were undertaken, such, for instance, as city railroad lines: and the result of all these favorable circumstances was the attraction to, and permanent establishment in, Buenos Ayres, of a vast number of people from foreign countries and from the other provinces of the republic. The influx of strangers at that time amounted to two-thirds of the balance of 47,716 mentioned in the table, that is to say, over 30,000 new inhabitants, which is equivalent to three and one-fourth times the usual rate of increase. Such an excessive augmentation of numbers, at a time when the city was not suitably prepared to receive them, or to afford them necessary accommodation, gave rise to an accumulation altogether incompatible with the general good health, and contributed, beyond all doubt, to the awful severity of the epidemic of 1871, by which more than 12,000 foreigners were carried off.

The yellow fever committed its ravages in the midst of an overcrowded city. But, notwithstanding the great mortality, there still remained,

with a surplus for the following year, a mass of inhabitants greater than would have been obtained by calculation, adopting the established annual rate of increase, and to which should be added the number of the immigrants of 1871 who settled in the city. These remarks may serve to meet the first objection above alluded to.

As for the second, suffice it to state that, in 1872, the tide of immigration again began to flow, and foreigners arrived in such numbers as to leave a balance of 34,235; and that in 1873 immigration reached the highest figure ever attained in South America, leaving a balance much more favorable still than that of the year immediately preceding; I deeply regret that I have not at hand the official returns to offer in support of this statement. In 1874 and 1875, by local causes easily explained, and others of a general character which have produced and still produce such grave perturbation in commercial and industrial circles throughout the world, immigration to Buenos Ayres was considerably diminished, while emigration was increased in a proportionate degree. There has, nevertheless, been no instance as yet, even at the worst, of the departures having exceeded, or even equalled, the arrivals; a balance, however small, still exists in favor of the latter. Now, taking into consideration the excessive accumulation which occurred in the two years immediately preceding the crisis, the same reasoning may apply to 1874 and 1875 as we have already applied to 1871, with the favorable difference in the case of the two former years that they were marked by no such catastrophe as the epidemic of the latter, to exercise a depressing influence upon the population. Hence, the adoption here of the mean annual rate which served us in estimating the number of inhabitants for the earlier periods, would seem perfectly justifiable; and we may, without any fear of exaggeration, set down the population of Buenos Ayres in 1875 at 230,000.

This population is spread over an area of 1620 hectares (or 6 square miles approximately), or a mean of 70 square metres (= 833 square yards) to each individual. Of course, the distribution is not always uniform. There are many districts much more densely populated than others, and the tenement-houses, though disseminated through all the districts, are in themselves centres of accumulation, pernicious alike to the physical and moral well-being of the community. The streets are for the most part narrow, barely eleven metres in width; and the public squares are few and of inconsiderable dimensions. Within the last few years, a vast system of horse-railways has been introduced, with an aggregate length of seventy miles, by means of which cheap mode of conveyance a certain degree of expansion is afforded to the inhabitants. It may here be ob served that, with the exception of Philadelphia, Buenos Ayres has, in proportion to its population, a greater extent of horse-car lines than any other city in the world.

From this short history of the development of the population of Buenos Ayres, it may be presumed that it is largely composed of foreign elements. Indeed, the census of 1869 shows that, in that year, foreigners constituted almost one-half of the total number of inhabitants.

Doubtless the proportion of foreigners has increased in a marked degree since that time, and, in the absence of precise data, I calculate that their number in 1875 exceeded that of the natives as follows: