is principally for the purpose of slaughter, and time is not afforded for their development. Indeed, those causes which produce pneumonia under ordinary circumstances also produce the disease in question.

Contagion has been alleged as not only a cause of the disease, but as the principal cause. The evidence upon this point is exceedingly contradictory, and yet it is obvious that it is one of the most important questions, so far as the prevention or extirpation of the disease is concerned. The spread of contagious diseases being under control, while those which follow the laws of epidemics are very slightly if at all prevented from spreading, except by placing the animals under circumstances which would prevent the production or spread of disease generally, - such as good food of a sufficient quantity, and cleanliness, with proper ventilation, protection from the intemperature of climate, and especially avoiding overcrowding.

There are difficulties in examining the question. The tendency is to assume a contagious origin of disease, especially if its nature is obscure, besides which, if it is prevalent and severe, and produces a panic among the observers, their statements must be taken with caution. One of the reasons for the general assumption of a contagious origin under these circumstances is, that it is considered a complete explanation in a single word. But it must be remembered that there are two conditions necessary for the propagation of contagious diseases, a contagious property in sufficient concentration, and a predisposition on the part of those exposed. Erysipelas, under ordinary circumstances, is non-contagious; under others, it is believed to be decidedly contagious. Even small-pox requires peculiar conditions for its extensive spread, otherwise it would be equally prevalent at all times, instead of exhibiting an outbreak at considerable intervals of time. Contagious diseases rarely arise spontaneously, and such occurrence would be evidence against contagion. Epidemics, on the other hand, make their appearance in widely separated places, so nearly at the same time as to preclude the probability of contact. But once having appeared, they have a progress which much resembles that of contagion, and may easily mislead careless or incompetent observers. A few years ago, a person sick with cholera was brought from a neighboring town, where it was then prevalent, among friends living upon a wharf in Brighton, where the predisposing causes - bad ventilation, overcrowding, and filth - were well marked. The person died, and within fourteen days eleven other cases followed, five of which proved fatal; one of these was of a cabin-boy on board a vessel lying at the end of the wharf. Here, one might say, is unquestionable contagion, no cases having existed within several miles. But one of the persons ill of cholera was carried from this place to an open, well-ventilated house, a quarter of a mile distant, and although as constantly visited by friends, and, so far as contagion went, as favorably situated for the communication of the disease as in the former instance, not one contracted it. Here the argument was as strong upon the other side. Many facts of this kind have been observed in various places, as well as others of a different character, but all tending in one direction; and hence the now established belief in the non-contagious nature of cholera. Unfortunately for our knowledge of the disease in question, no experiments were made as to its mode of communication. It is obvious that had such been tried, all complications could have been excluded, and decided results obtained. First, healthy cattle could be sent into an unhealthy barn among diseased cattle; and, secondly, a diseased animal could be sent to a healthy barn among well cattle. If, in the first case, the cattle became diseased, it would, so far as it went, prove that a cause of disease existed in the animals, or the locality, or both; and, in the second, that a cause sufficiently powerful of itself to produce disease existed in the animals,

*Swine brought from the Western States are exceedingly liable to fatal pneumonia soon after their arrival in the Eastern cities; and although it spreads rapidly when once it appears in a herd, it is not deemed contagious.

that is, that the disease was contagious. Instances of both these conditions, though perhaps not sufficiently numerous or sufficiently uncomplicated to settle the point, are believed to have occurred in the course of the disease in Massachusetts.

It is generally assumed that the only animals that can be affected by Pleuro-pneumonia belong to the bovine class. But contagionists say it can be transmitted by the application of the contagious matter, either directly by contact or indirectly through a considerable intervening space. Its vehicle in the latter case is the breath, which derives its material of disease from the inter-lobular cellular tissue of the lungs. It adheres to living and dead bodies, to rough, woolly, hairy bodies, such as straw, hay, clothes of men, coverings of animals of the bovine class, and perhaps every other species of animals. The walls of barns are essentially the bearers of contagion, and continue to be such even after all trace of the original vehicle of the disease has vanished. It can increase its power when once introduced, so that from one case it can reproduce and multiply itself until it has affected hundreds upon hundreds of individuals. Still more, a piece of clothing which has become infected may infect another piece with which it is in contact, and this last thus become a bearer of disease. The disease also sometimes becomes fixed in a locality, and that when this locality is of very limited extent. It has a great tenacity, and the animal retains the power of communication, not only through the feverish stage, but during the subsequent non-feverish condition, extending through eight or ten weeks after the cure has apparently been accomplished. The influence does not necessarily attack those nearest, but often falls upon those which stand at a distance; some animals resist for a long time, finally yielding, while others resist permanently. Such are the views set forth by a firm believer in the contagious nature of the malady. (Kreutzer, p. 337.) Delafond (p. 213) thinks that the disease presents all the general characteristics of contagious diseases, and has collected a considerable number of instances of diseased animals introduced into herds, in stalls, and in the fields, in which the introduction was followed by one or more cases of a similar disease. But his opinion does not agree with that just cited as to the power of those who touch, approach, or take care of diseased animals, to transmit the disease to healthy animals by the same proximity and care. Neither does he consider it proved that animals of different species may be the means of transmitting the affection; he believes that many of the accounts of subtle contagion are entirely fabulous, and that the elements of contagion do not spread to a great distance from the sick, and are by no means of the same activity as the elements of typhus and other well-known and admitted contagious diseases. In investigating the period of incubation, or the time which elapsed between exposure and the appearance of the disease, fifty cases have been collected in which the moment of exposure and that of the development could be satisfactorily determined. From which it appears that the period in question was,

Hence we see that nearly four fifths of the whole number fell sick between the fifteenth and twentieth days and nine tenths before the last-named day. It is also to be observed that the variation in the period of incubation from six days to sixty is without analogy in any other contagious disease.

Those who oppose the view of contagion see a sufficient cause in the combined influences previously mentioned as having a great bearing upon its course and upon its development in a locality. They believe that the atmospheric conditions and those circumstances, of a character but little understood, leading to the spread of epidemics generally, are also in action in this. But it is denied that the disease bears any relation to those which are well

known to be contagious, to the contagious typhus, on the one hand, or to glanders or diseases having a local expression, on the other. Still less does it resemble sheep-pox, or any eruptive disease of animals. Neither has it been made to appear that any affection of the lungs or pleura in man or horse or swine or dog ever shows any contagious property. It is admitted, by contagionists and non-contagionists, that the disease may and does arise under circumstances which preclude the probability of any contagion, unless we admit an intensity and persistence in its elements which are abundantly disproved by the non-communication in cases much more favorably situated, that, in fact, the disease arises spontaneously. If it arises spontaneously, then the circumstances for its propagation, if contagious, are the most favorable possible, and the disease should spread with the greatest certainty and rapidity; but this certainty and rapidity have not been observed to accompany spontaneous development. The history of the disease in Holstein shows that the strictest measures and most careful destruction of all existing disease did not prevent its continuance or recurrence after a very short interval. It was very apt to recur in nearly the same locality, endemic, when no evidence could be brought forward to show an introduction from abroad. The following experiments will show how great is the power of resistance under the circumstances stated. "I wished," says Dietrichs (Delafond, p. 227), "to ascertain whether the emanations which escape from animals ill with peripneumony can transmit it to healthy animals placed beside them. To this end I obtained a cow five years old, and assured myself of its perfect health by examining it while eating and drinking, and by making it cough by pressing the larynx, and placed it between two oxen with peripneumony. Those two animals were in a small stable, and so fastened that each could reach the food of the other. The oxen ate very little, being in an advanced stage of the disease; the cow, on the contrary, ate not only the intentionally small quantity of food given her, but also ate that which was covered with the mucus from the nostrils and the saliva of the oxen. This cow was left in this condition for two days, when she was returned to her former stable, and was replaced by another, also healthy. This last remained with the oxen a day and a half; when one of the two died, she was left with the survivor two days and a half longer. The ox was then killed, and the autopsy proved the existence of well-marked peripneumony." The results of these experiments demonstrated non-contagion.

The following experiment by a competent observer was tried in France. Pleuro-pneumonia was rife in Bligny, and Gaullett was sent by a government official to investigate it. "I separated the discased from the healthy animals, although in my judgment it is not a contagious disease. To establish my opinion, I tried an experiment at my own risk; I bought a healthy cow six years old, in a neighboring commune, where the disease was unknown, and drove her to Bligny and put her in a stable with a cow and ox attacked with the epizootic, and deemed incurable. The healthy cow was placed between these two animals, the ox on the right and the cow on the left. The first died three days after the commencement of the experiment, and the cow in five days. On opening the ox I took the serous and purulent matter, still warm, and, making a vertical incision two and a half inches long between two of the ribs of my cow, I detached the skin with the bistoury and introduced into this broad wound beneath the skin a pledget wet with the purulent matter, and secured it with a bandage. I kept the animal two days on solid food. During this time a considerable tumefaction appeared about the inoculated wound, accompanied by great sensibility; some days after an eschar formed and was detached, the wound was dressed with a digestive; the engorgement soon diminished, and in less than fifteen days the wound was healed.

"This animal experienced no indisposition. I sold her to a man who kept her two years in good health and flesh; but not being a good milker, he sold her to a butcher. When she was killed I assisted at the opening, and found the organs of the chest perfectly healthy."

Nine animals were inoculated with the nasal mucus, and with saliva from diseased animals, without any other effects than those which usually follow the introduction of foreign matter derived from other sources; no evidence of Pleuro-pneumonia followed. To this Delafond objects, that it is not proved that the matter used was expectorated, it might have been from the nose only; this objection, however, will hardly avail when we remember that the expired air is assumed by the contagionists to be the vehicle of contagion, and that it adheres to whatever moist, or even dry substance, with which it comes in contact.

The "Mark Lane Express and Agricultural Journal" for October 8, 1860, has a report of a recent meeting of the Ipswich Farmer's Club, at which Pleuro-pneumonia was discussed, and the opinion of several of the members obtained with regard to contagion. Instances were given in which its origin was believed to be spontaneous. Mr. H. Biddel referred to a dairy of nine cows kept by him some years since. They had all been on the farm several years, with the exception of one, which came from a farm where the disease had never been known. The disease broke out, and the whole either died or had to be slaughtered. Another member had known a lot of bullocks bought at a fair, and when they were brought home, divided into three different lots, and sent to three different farms; two lots were visited with the disease, the third entirely escaped. In another case a lot of thirteen was bought; the disease appeared, four or five had to be slaughtered, and the rest were immediately sold; they went to a farm about four miles distant, where they were fattened and did well. Prof. Simonds, whose report has already been quoted, still considers the disease contagious, but admits that it differs from all others in this respect, that the morbific matter is in some cases a long time dormant in the system, and can be got rid of by purgatives and diuretics, and that these means, with stimulants and iron, and generous feeding, will often rid a herd of the disease. This statement would indicate an origin quite different from any known contagion.

"On the banks of the Almond, in the county of Mid-Lothian, are situated three farm-steadings, about 600 yards from the river, upwards of 60 feet above it, and 360 above the level of the sea, with a good southerly exposure. Milch-cows are kept in the two westmost steadings, and feeding cattle in the eastmost. About eight years ago, in the autumn, the cows in the westmost steading were attacked by Pleuro-pneumonia; fiercely and fatally it raged among the stock for about two months, till the number of empty stalls in the byre showed the sad havoc which had been committed, and which the farmer did not think prudent to repair at the time. Though there was no communication held between the adjoining steadings, the disease made its appearance among the stock in the next steading, a few weeks after it had commenced in the former one. After decimating the cows here also for some time, it attacked the feeding cattle of the eastmost steading, among which it continued more or less throughout the winter. The cattle, both in courts and byres, were attacked by it; and it is worthy of remark, that some weeks before the feeding cattle were affected by the Pleuro-pneumonia, the murrain went through the whole stock. Now it is somewhat curious, that during the whole of that autumn and winter the disease lingered amongst the cattle in these three steadings, and never, in one case, travelled beyond them north, south, east, or west. In connection with the steading where the feedingcattle were kept there was another steading, where about twenty cattle were fed in courts, at a distance of half a mile from the former steading, at a much higher altitude, and considerably more exposed. Not the least precaution was taken to prevent any communication between the different lots of cattle in the two steadings; on the contrary, the same servants fed them, and on the disease breaking out, all the cattle at the two steadings were bled by the same men on the same day. Not one of the cattle in the upper steading was affected by the disease, while most of those in the lower one were sold off after being attacked. Last summer, on the same farm, two lots of

cattle were grazing, the one on the fine sheltered haughs at the side of the river, the other in an exposed field beside the upper steading, about 150 feet above the river. One after another of the cattle on the haughs were attacked by Pleuro-pneumonia. The farmer, finding that none of his other cattle were affected, thought that the disease arose from the great differences of temperature to which the cattle were subjected during the day and at night. During the day, the temperature was very high in the haughs, as they were mostly surrounded by woods, and the sun beat upon them; at night a cold chill air rose from the river. He accordingly removed the cattle from the haughs, and put them beside the others in the exposed field. There was not another case of Pleuro-pneumonia on the farm during that season. In none of the cases narrated above could the disease be traced to infection. Again has it broken out in the district without any assignable cause, excepting atmospheric; but we are glad to say, that, though its ravages are as extensive as ever, the attacks are by no means so virulent, and there are more cases of recovery than formerly." Journal of Agriculture, London, July, 1858. If we now turn to the origin of the disease in Massachusetts, we find that the first animal which sickened could not, by a possibility, have been exposed to any animal ill of the disease within seventy-five days, unless we suppose the two cows which died from the effects of ill treatment and the hardships of the voyage were affected by it. Of this there is no evidence; on the contrary, we have the opinion of those who had the care of them, and subsequently became familiar with the symptoms, that they had no reason to believe that they had any affection of the lungs. There is no reason to believe that the disease previously existed among other cattle of the herd, and we are therefore compelled, in the absence of other facts, to admit that it remained dormant seventy-five days, or that it arose spontaneously in Belmont. But if we remember that, of the fifty cases cited, not one became ill later than sixty days after exposure, we must consider the latter supposition the most probable. That the disease did not propagate itself in the open air seems probable from the fact that the two calves which sickened and died, the one with the herd, and the other a few days after, did not communicate it to the nine which occupied the same pasture. So again, the fact that the neighboring animals did not become diseased, although for several weeks, when the epidemic was most virulent, no care was taken to prevent communication. The fact that an animal placed in the barn with sick animals became diseased, and another taken from that barn did not communicate disease to those with which it was subsequently placed, also points to the probability that a much closer and longer continued exposure in the diseased locality itself is required for the development than was at one time supposed.

The outbreak of the disease in Brookfield upon the introduction of the calf from the Belmont herd has, on the other hand, more of the appearance of contagion. But the evidence would be much more conclusive if the facts were definitely stated; we know but little more from the evidence taken before the Legislative Committee, than that the animal was sick. That animals became sick after the introduction of the calf is unquestioned, and it may be in consequence of such introduction; but it is a question whether the outbreak did not occur in consequence of certain conditions existing in a limited territory, whether, in fact, it was not analogous to the cases of cholera above-mentioned. If the conditions under which the disease was supposed to be communicated had been studied carefully, the question of contagion could have been much more easily settled. But we have only the general statement, that all animals diseased could be traced to an exposure to others also diseased. The exposure was very different in different cases; in some cases, it was standing in the same barn, in others, passing a barn where there were sick cattle. The case following the death of the calf oc curred in a fortnight, and others again once a fortnight, until eight were lost in a herd of forty; and these were all that were lost from that herd, although all were equally exposed for the four days the calf was there.