tially necessary conditions, heat and moisture, in the production of the morbific effect, we have no positive knowledge, nor would the discussion of the various hypotheses that have been framed in relation thereto, inure to any practical good. It may supply the material out of which a poisonous gas is formed, as maintained by some, or it may prove a nidus or hotbed for animalcules or vegetable germs, (1) according to the theories of others. Some, I must here take occasion to remark, attribute the poison to subterranean exhalations, to the gaseous effluvia from a volcanic soil. Still others deny any specific cause, or, again, believe it to consist in an accumulation or modification of the electricity of the earth and the air, although none of these views have been as yet established by sufficient proof; still we know the conditions that are necessary to give efficiency to the toxic agent, from whatever source it may be derived. As long as these conditions co-exist, certain effects are produced-interrupt, counteract their co-efficiency-and the probability is we may rid ourselves, to a great degree, of the annual recurrence of malarial fevers.

MODIFYING AND AMELIORATING CIRCUMSTANCES.

From the foregoing cursory examination of the conditions under which malarial fever has been developed in California, I hasten on to a further consideration of some of the circumstances and peculiarities attendant on its appearance here, and which have also been found by experience every where capable of controlling its evolvement or production.

Cities and large towns, it is well known, seldom suffer from malarial fever, and are to be considered as in some degree presenting opposite conditions to a sparsely settled country. As the buildings extend out, and the closely inhabited portions expand, and by so doing lessen the area of humid and exposed soil, the disease recedes. The medical history of New York, Buffalo, Auburn, Syracuse, Philadelphia, Charleston, Savannah, Louisville, etc., illustrates this. The statements of

(1) This theory, says Dr. H. Von Ziemssen (Cyclop. Prac. Med., Vol. II, p. 585), has been brought forward again, of late, by various observers. Thomas (Archiv f. Heilkunde, VIII, p. 225). Scoda (Clinique Européenne, 1859, Canst. Jahresber, 1859, IV, p. 73), believes them to be either living or in a state of decomposition. Baxa (Wien. Med. Wochensehr, 1866, p. 78), saw low, cell-like structures in drinking water. Balestra (Compt. rend., LXXI, No. 3, p. 235), discovered a species of algae in the Pontine marshes. Salisbury (Amer. Journ. Med. Sc., 1866, Jan., p. 51), found in his investigations in the valleys of the Ohio and Mississippi, that the sputa of the sick contained small elongated cells, presenting themselves singly or in rows, which he considered to be alga-cells of the species palmella. These he also found and collected on glass plates set up over marshy ground, and in great quantities on the clods of an upturned marshy ground. According to his observation, these alga-cells do not rise over one hundred feet above the level of the sea. He was able to produce the most intense attacks of intermittent fever by means of the fresh clods, if allowed to place them within the open window of a sleeping room in a house lying about three hundred feet high. The attacks, in four persons, the subjects of two experiments, followed in ten, twelve, and fourteen days, and were broken up by quinine. Hannon (Journ. de Med. de Bruxelles, 1866, Mar., p. 497), says that when he was devoting himself to the study of the sweet water alga, during their fructification, he was attacked with an intermittent fever of six weeks duration. In opposition to Salisbury, Harkness, of Sacramento, states (Boston Med. and Surg. Journal, 1869, Jan. 14th), that he has found the palmella spores in the snow, and at the summit of the highest of the California Alps, and claims that they may very readily become mixed with the saliva and the urine from without-at the same time having nothing at all to do with malaria. Nevertheless, Ziemssen states that, on the Tuscan Appenines, fevers are to be found at the height of one thousand one hundred feet; on the Pyrenees, at five thousand feet; on the island of Ceylon, at six thousand five hundred feet; and in Peru, at ten thousand feet, and even eleven thousand feet.

Professor Yandell, relative to the last named city, are so apposite that we cannot refrain from quoting them in confirmation of our remarks. "The rock, of which the subsoil is composed, forms a surface remarkable for its evenness; and the soil which it produces, as it crumbles under the action of the air, frost, and water, is peculiarly retentive of moisture. Ponds and slushes are abundant wherever the black slate constitutes the surface rock. The first houses erected at the fall, were built in the midst of ponds. Louisville, while it stood amid its ponds, was regarded as one of the most sickly towns in the Valley of the Mississippi. It was commonly called the 'graveyard of the west.' Intermittent fever was a regular annual visitant, and occasionally a form of bilious fever prevailed, rivaling yellow in malignity, and threatening to depopulate the town. The ponds have all disappeared-the streets have generally been paved, and though the grading is defective, and can never be as effectual for drainage as it might be rendered on a less even surface, still it is such as to carry off the rains into the river and the ditches south of the city. The only parts of Louisville (now) obnoxious to the charge of unhealthfulness, are its suburbs."

Now, with regard to Sacramento, whatever of reason there may be in the opinion formerly advanced by me, that the so-called cholera of eighteen hundred and fifty-two, when the city was in a transition-stage between country and a filthy, ill-conditioned town, traversed in all direc tions by sluggish, stagnant sloughs, was nothing more than a highly malignant form of malarial fever, there certainly, since a better order of things obtains, has not been witnessed, to the best of my knowledge, a single case of malignant fever within the city proper. All of the cases since met with here, have been of the simple intermittent variety, originating in the suburbs, and especially in that portion bordering on the American River, (1) where the amount of deposit is enormous.

That this modification, or mitigation, of the grave forms of malarial fever formerly met with is attributable, in a great measure, to the agency of similar sanitary measures to those just alluded to, respecting Louisville and other cities, will, I think, not be questioned by any one at all acquainted with the relative condition of the city then and now. In addition to the raising of the streets with sand above high-water mark, the better draining of the city, the filling up and damming of the sloughs against the ingress of water from the river, and the extensive building of houses, which intercept the action of the sun in low parts,

(1) Some idea may be formed of the immense amount of deposit brought down from the washings of the auriferous soil, above alluded to, when I state that on my arrival in Sacramento, in eighteen hundred and fifty, a large brig, named La Grange, was anchored in the middle of the mouth of the American River, to serve the purpose of a prison. Where that brig was anchored, there is now a road; what was then the mouth of the American River being completely filled up.

We are not aware that a sectional area-admeasurement of the Sacramento River has ever been made, but estimating the amount of water which passes down the river each second, during freshets, at three hundred and twenty-seven thousand six hundred cubic feet, we find, on an average, that there are carried in suspension past Sacramento City (a certain portion being deposited, as is shown by the elevation of the low as well as the high water marks on the rain gauge) thirty-eight thousand seven hundred and seventeen tons every hour, more or less, according to the stage of the American River-this affluent, owing to mining operations, being always most charged with detritus. The solid material, thus ascertained to be suspended in the water, is found on calculation to be sufficient to cover, in one year, a square mile, to the depth of two hundred and fifty-six feet. With these facts before us, it would seem that, if ever the etiology of epidemics and endemics is to be solved by the present methods of topographical and meteorological research, the Sacramento River, with its tributaries and influences, must be paramount in unraveling the enigma of the diseases of its basin.

there has been a very general cultivation of shrubbery, and plantation of shade and fruit trees in the streets and gardens. From what has been observed respecting the protective power of trees and forests against malarious diseases, it cannot be doubted that this extensive arboriculture has exercised a powerfully controlling influence.

Besides shielding, from the solar rays, the humid surface of the earth, trees have been supposed, from the time of Pliny, to absorb insalubrious exhalations. Their beneficial effects are, we think, to be accounted for in this way more reasonably than by the obstacle or mere physical obstruction they offer, like a fence or wall, as conjectured by Lancisi and others. This opinion," says Dr. R. La Roche, in his erudite treatise, controverting the supposed connection of pneumonia with autumnal fever, "this opinion has, to a certain extent, received the sanction of Thouvenelle, Copland, and other modern writers; and its correctness is rendered probable by the results of certain experiments made long ago, and repeated more recently to ascertain the fact." "Plants," says Julia de Fontenelle, "which Priestley had inclosed in glass jars filled with vitiated air, continued to thrive, and, at the end of a few days, this air had become as pure as that of the surrounding atmosphere." Dr. Lewis, of Mobile, adverting to the subject, remarks: "It is the generally received opinion, that living vegetation protects the human system from the deleterious effects of malaria; and reasoning by analogy, it would appear that experiments, made by scientific men, have satisfactorily explained the mutual dependence of the animal and vegetable kingdoms on each other for support. It has been ascertained that if air, rendered pernicious by respiration, be confined in a bottle into which some green plant has been introduced, and exposed to the action of the sun, the carbonic acid will be absorbed and the air restored to its original condition. The putrefaction of animal matter, and the decomposition of vegetable substances, would cause a sufficiency of carbonic acid vapor, when united with atmospheric air, to destroy every living being, were it not for this wise provision of nature. This gas, which is poisonous to the human as well as animal species, is a source of nutriment to every variety of plant; and thus, it would appear, exercises a benign influence in protecting men from the deleterious effects of poisonous vapors." "And if the effect," remarks La Roche, "is obtained, so far as regards one species of poisonous vapors, it may be equally so in reference to that giving rise to fever."

Many facts could here be collected, if the limits assigned to this article did not restrict me, to show that certain trees and vegetable productions, growing in damp, swampy, and malarial countries, possess the property of disinfecting them. The delta of the Mississippi, from the latitude of New Orleans down to the Gulf of Mexico, and west of the city, to its termination on the further side of Bayou Teche, abounds in lakes, and is traversed by a great number of small bayous. Herein are included the fine and flourishing settlements of the La Fourche, the Teche, and the Attakapas, all of which appear to be as little affected with autumnal or yellow fever as the Mississippi coast above the city. Nearly the whole surface of many of these bayous, and a considerable surface of many of these lakes, are covered in a greater or less degree with a great number of aquatic plants, both phænogamous as well as cryptogamous; but more especially with a large flowering plant, known by botanists under the name of Jussieua grandiflora, which grows three or four feet above the surface of the water, and gives the fallacious appearance of a natural meadow. To the influence of this plant Dr.

* * *

Cartwright ascribed the immunity of the region of country, where it grows, from fever; and adds, "I could find no other cause for the remarkable purity of the stagnant water in the lagoons, swamps, lakes, and bayous of lower Louisiana. North of the region where the Jussieua grandiflora flourishes, there is the same kind of alluvial soil, formed by depositions of the identical rivers which form the soil of lower Louisiana; yet stagnant water, in hot weather, becomes exceedingly impure, beyond the limits in which the plant under consideration is found. The soil, therefore, cannot occasion the purity of the water of lower Louisiana, because the same kind of soil, a little further north, has not the same effect. I think it may be fairly inferred, therefore, that the aquatic plant consumes or feeds upon those substances which, in other situations, corrupt and vitiate stagnant waters in a warm climate."

It is not important to the point in view to know positively whether the healthfulness of the country just considered is due exclusively to this plant. The experiments of Maury with the sunflower (helianthus) go to show that other plants possess the same disinfectant property in malarial regions. But I allude more especially to the circumstance because of its relation to another fact of the same import in California. It was seen in our topographical sketch that the borders of the draining streams of the Sacramento Valley, especially near their point of exit, are marshy and overgrown with a wide expanse of tulé (scirpus lacustris.) This species of bulrush is very luxuriant, often attaining the height of eight to ten feet, and seldom less than six feet. It literally covers the swampy lands, and particularly all that extensive delta (as may be seen on the accompanying topographical map), formed by the union of the San Joaquin and Sacramento Rivers, before finding their way into Suisun Bay, at a break in the coast range. So far as our information extends, these tulares, or marshy lands, are exempt from malarial dis

eases.

A remarkable fact, specially worthy of insertion in this place, is one recorded in Sullivan's visit to Ceylon. "A large fresh-water lagoon, of a most green, slimy, tropical appearance, producing in abundance a lotus of almost Victoria Regia magnificence, stretches away to the back of the fort, and around are situated the bungalows of many of the Colombo merchants. The propinquity of this lake would, in any other tropical country, be considered as insuring a considerable amount of fever to the neighborhood; in fact, I doubt whether any advantage would induce a West Indian to locate in such position.

"However, in the matter of climate, Ceylon stands per se, and offers a total antithesis as regards the healthiness of certain districts of most other tropical countries. Whilst the vicinity of tanks and lagoons of the most fetid and aguish character is perfectly healthy, that of rivers is equally deadly. The apparent contradiction of the usual laws of nature is accounted for by two reasons. The tanks are covered with various kinds of aquatic plants, which, by a kind of providence, are made to serve not only as filterers and purifiers of the water itself, but even as consumers of a considerable portion of the noxious exhalations that would otherwise poison the neighborhood. The banks of the river, on the contrary, are rife with fever. The cause assigned is, that during the rainy seasons they swell to great size, and collect the vegetable matter of a large extent of country; but owing to the rapidity with which they fall at the commencement of the dry season, and the winding and intricate nature of their course, the streams are unable to clear

themselves, and this accumulation is left to decay in its bed and infest the surrounding country. There exists also another reason: the beds of the Ceylon rivers are almost invariably composed of sand, and the stream, instead of sweeping down the decomposed vegetable matter it holds in its waters, as must be the case in hard-bedded rivers, percolates through the sand, leaving the poisonous matter on the surface exposed to the burning rays of the tropical sun." As correlative, and calculated likewise to establish the protective power of trees also against malaria, I would mention in this connection another fact that once came within my own personal observation: Some thirty-five years ago, the streets of Charleston, South Carolina, were characterized by a very general growth of old umbrageous Pride of India trees (Melia Azedarach), whose cleanly verdure, free from, because poisonous to, insects, was as refreshing to the sight as the shade was grateful to the feelings during the almost tropical heat of the Summer months. But with the influx of northern merchants and Yankee enterprise came also the spirit of innovation, and this beautiful feature of one of our oldest southern cities was doomed to eradication by an ordinance of the City Fathers.

The very first Autumn after the extermination of the shade trees, the city, which had for many years enjoyed a perfect immunity from yellow fever, was afflicted with one of the most severe epidemics, and has been more or less subject ever since to an occasional return of the disease.

A distinguished natural philosopher-Changeux-inferred from the results of his experiments, that the action of trees and living vegetation in the production of the effect under consideration, is twofold. "Plants," he says, "whether odoriferous or inodoriferous, give issue to emanations which, when mixed with poisonous vapors exhaling from marshy or damp soils, neutralize their pernicious influence. But the former exercise a greater effect through means of the neutralizing process than by the power of absorption just mentioned, their emanations mixing with the air we breathe, and correcting its deleterious properties by virtue of the particular qualities with which they are endowed. The second class the inodoriferous-on the other hand, act more, evidently, through the means of their power of absorption than the neutralizing property of their emanations, and remove from the air the vapors by which it is contaminated."

Senebier, in his Physiologie Vegetale, and other expert observers, ascribe the disinfection, not to the absorption by trees and other vegetable productions of the gaseous poison floating in the atmosphere of malarial localities, but to the purification of such an atmosphere through means of the large supply of oxygen obtained from living plants, and the neutralizing agency of that gas on the mephitic particles it meets with in insalubrious places. As to the manner in which the oxygen thus produced destroys or prevents the elaboration of the malarial poison, some difference of opinion exists. M. Carriere, in his excellent work Le Climat de l'Italie sous le Rapport Hygiènique et Médical, adopts the views of Chevreul and Fontaine, in relation to the formation of the febrific poison through means of the action of organic matter on the sulphates contained on the earth, or in water, with the aid of the oxygen derived from the former. According to Carriere, the leaves of plants, and of trees, as well as the green substances that cover the soil, are all inexhaustible sources of oxygen, which is so important to sustain life and preserve health. This fluid, thus furnished, offers an obstacle to the

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