In another experiment the animal had convulsive motions all over immediately after the injection, followed by a lethargy. Next day a carbuncle appeared on the great pectoral muscle on the right side. On the third, a bubo appeared on the thigh, and the same day the dog died. From the time of the injection he had neither eat nor drank. On dissection the fore part of the breast under the teguments was found entirely gangrened, the inward parts and viscera full of black clotted blood, the outward surface of the lungs was all purple, the heart was swelled as big again as usual, and the four cavities were full of black clotted blood. The bile of this dog, injected into the crural vein of another, produced similar symptoms, only the latter eat a little boiled meat, which he vomited up again in two hours. He died the third day, with the same symptoms of the plague as the others.
The bile of people who died of ordinary malignant fevers was much less powerful. A quantity (not mentioned how much, but probably a drachm) mixed with four ounces of warm water, was partly injected into the jugular vein of a dog, and a compress soaked in the rest of the liquor applied to the wound. He appeared heavy and sleepy, and would neither eat nor drink till the third day, when he did both willingly. On the fourth day the compress fell off, the wound was found to be diminished one half, and healed by degrees, the dog recovering perfectly. In another experiment with the bile of a patient who had died of a malignant fever, the dog not only had about a drachm of it put into a wound in his thigh, but was made to swallow some of it; notwithstanding which he was not seized with any distemper, and the wound healed in fifteen days. This bile was as black as ink, in great quantity, and very thick. In the other subjects it was of a deep green. In another experiment, with the same bile applied on a compress, the dog likewise escaped without any apparent disorder; but in a third, the animal died in twenty-three hours, though at first he had shown no sign of being affected, only that he seemed to be thirsty, and drank with greediness. On opening him his heart was found still to beat with violence, and, after the beating ceased, no blood was to be found in it, either in the auricles or ventricles. “This liquor, crowded together in the great vessels, appeared of a lively red, and very fluid, without any of those concretions that we constantly observed in those who died of the plague. Here appeared neither external nor internal marks of the plague.” The bile of a person who had died of an erysipelas, injected into the crural vein of a dog, produced no bad effect. A dog was killed by half a drachm of Hungarian or blue vitriol injected into the jugular vein. He died in universal convulsions: the heart was full of grumous blood, reduced to a kind of thick pap, but without any clots. The bile, applied to two wounds in another dog, produced no bad effect.
From other experiments it appeared that even the pestilential poison itself, taken into the stomach of dogs, did not produce any deleterious effects. “A dog of the Hospital of the Mail in Marseilles, who followed the surgeons when they went to dress the sick, used greedily to swallow the corrupted glands, and the dressings charged with pus which they used to take off the plague sores: he licked up the blood that he found spilt on the ground in the infirmary; and this he did for three months, being always gay, brisk, well, full of play, and familiar with all comers.” The health and briskness of this unfortunate dog proved his ruin, by making him the subject of philosophical experiment. A drachm of the pestiferous bile injected into the crural vein, killed him in four days. He had a considerable hæmorrhage from the wound the night before he died, and he had also a disagreeable smell both while living and after he was dead. Two other dogs, which had swallowed a quantity of pestiferous bile, became heavy and melancholy, refused their food, and showed other signs of disorder; but all these went off in a short time, and no signs of the distemper appeared.
These experiments induced M. Deidier to suppose that the contagion of the plague lay only in the bile; but the following experiment shows that the blood was equally infected, and capable of communicating the disease, and that of the most malignant species. It was made by M. Couzier, physician to the infirmary at Alais, and in the Philosophical Transactions we have the following account: “I took a quantity of blood from a person dead of the plague, and mixed it with warm water, which mixture I attempted to inject into the crural vein of a dog, but the end of the syringe being too large to enter the vein, the experiment did not succeed. This made me resolve to try to lay some of the same infected blood upon the wound. This I accordingly did, and covered it with a dressing, which the dog got off in the night. I found the next morning that the dog had licked the wound, and that he refused his food. Towards night he began to bemoan himself, and gave signs of an approaching death. The next morning I found him dead, the wound being considerably swelled and gangrened, and the edges round the swelling were likewise gangrened.
“Upon opening the body, we found the liver something larger than usual, with spots of a livid purple, as in the bodies of persons dead of the plague. In the stomach was found a quantity of black coagulated blood, of the size of a hen’s egg. This in all likelihood was what he had swallowed upon licking the wound. The heart was very large, with a black grumous blood in the ventricles, and the auricles were turned blackish and gangrenous.”
This last experiment naturally brings to remembrance those of Dr. Home at Edinburgh, in which he inoculated the measles by means of the blood of patients ill of that disorder. From the accounts he has given in his treatise entitled Medical Facts and Observations, we can have little doubt that his experiments succeeded, however others may have failed. One thing, however, is very obvious, viz. that if we mean to communicate a disease by means of the blood, we must use a much greater quantity than if we make the experiment with the matter of an abscess. The case of contagious diseases seems to be the same as in fermenting liquors. With a small quantity of yeast we can easily induce fermentation in any proper liquor, but, if we skim off the yeast, and use only the pure fermenting liquor, we must use a much greater quantity; and to inattention to this circumstance we may with probability ascribe the difficulty which Dr. Home himself met with in introducing the disease, and the total want of success in others. In M. Couzier’s experiment a considerable quantity must have been used, as he says that in the dog’s stomach it equalled the size of an hen’s egg. A much smaller quantity of matter taken from a pestilential abscess is capable of producing the disease in a human body, as is evident from the case formerly quoted of that gentleman who inoculated himself for the plague, and of which Dr. Guthrie gives the following account: “This was Mathias Degio, one of the surgeons of the hospital at Bucharest, a building appropriated to the cure of the plague in the Russian army. He, perceiving the gentlemen of his profession condemned in a manner to death, if punctual in the discharge of their duty [103] had the resolution to inoculate himself for the plague, in the full confidence of its efficacy, and ever afterwards found himself invulnerable, whilst his companions around him were falling victims to its fury. He produced the disease by inserting, with the point of a lancet, under the epidermis of his arm, matter from a pestiferous abscess, and followed the cold regimen observed in the small-pox, as he had imitated its mode of inoculation. On the fourth day of the puncture the fever declared itself, and he, being perfectly devoid of fear, got through the disease without feeling more inconvenience than if it had been that which he imitated. He drank freely of cold water, with vinegar, or a little wine, and kept generally out of doors. This beverage was the only thing that had the appearance of medicine,” &c.
From a careful attention to all these histories, it is plain that the plague is naturally an eruptive disease, as, in all the animals in which it was artificially brought on, eruptions took place, provided the life of the creature was sufficiently prolonged to allow them to come out. Dr. Russel says, that, from his diary, he noted down the cases of two thousand seven hundred patients, all of whom had eruptions of one kind or other. In this it agrees with the small-pox, which Dr. Mead justly considers as an inferior kind of plague. In the latter, however, the eruptions seem to resemble those called by Dr. Hodges the tokens, only that the cause which produces them is less violent in its nature; but why the eruptions of the small-pox should be in distinct pustules, and not one continued boil all over the body, is undoubtedly inexplicable on any theory whatever. The same is true of the plague. No man can explain why the tokens, for instance, instead of being collected into one great eschar, are dispersed into small distinct pieces; or why, instead of buboes in the groin and armpit, or instead of carbuncles in different parts of the body, there should not be a single one equivalent in bulk and power to them all. This appears similar to the phenomena of rain, hail or snow, which fall in distinct drops, fluid or congealed, or in flakes, instead of being equally diffused all over the spot on which they fall. In the latter case we say that the phenomenon is occasioned by electricity: we may say the same, if we please, of the small-pox and plague, with equal emolument.
From the accounts we have just now quoted, it appears that there is between malignant fevers and the true pestilence a very essential difference; the latter tending to thicken the blood, the former to make it thinner. In this respect therefore the poisons seem to resemble malignant fevers very considerably; for M. Fontana observed that by mixing animal poisons with blood drawn from a vein, it was prevented from coagulating. In the instance above related where a dog died in consequence of bile injected into his veins from one who died of a malignant fever, the blood was found extremely fluid. In some who died of the hospital fever, Sir John Pringle informs us, that suppurations had taken place in the brain; but in the true plague the tendency to mortification always prevailed above every thing.
Lastly, that the plague proceeds from too great a quantity of heat, either emitted from the body itself, or some how introduced into it, seems to be pretty plain from the effect it has of augmenting the venereal appetite to an almost inconceivable degree. This was taken notice of in the plague of Marseilles, and indeed in many others. Russel quotes two remarkable passages to this purpose; one in a plague at Genoa, the other in Messina. “Amidst so many dreadful fears and terrors, amid so many fetid and putrefying bodies, amid the shrieks, the sighs and the groans of the sick, what would you have expected? That the people, struck with dread and horror, remained sad, modest and quiet. You are mistaken. They sung, played on instruments, danced, intrigued, and Genoa never was seen so shameless, debauched, and disorderly. I have said before, that God in this plague gathered in a harvest for heaven; but it seemed to be also a vintage for the lascivious of of the earth. If not so, how came so many marriages to be celebrated in the Lazaretto of Consolation, and that so many women, without shedding a tear for the death of their husbands, immediately entered into new engagements? One day, in particular, five marriages were performed, four of the bridegrooms being buriers of the dead, and dressing themselves and their brides in clothes stripped off from the bodies of the deceased.” On the plague of Medina he quotes the following extract of a letter written by a gentleman who resided in that city during the plague in 1743. “It has always been observed, that, after every plague, those who recover are addicted in an extraordinary degree to lewdness and incontinence, which was surprisingly visible at Messina, and carried to such a degree of frenzy and bestiality, that many were known to violate the bodies of dead virgins!”
That an extraordinary propensity to venery may be produced by introducing into the body a quantity of heat, admits now of a kind of demonstration from a fact mentioned by M. le Roy concerning phosphorus.[104] This substance is exceedingly apt to take fire on the application of a small degree of heat, and even by slight friction. It is now introduced into the materia medica, and is found to be a very powerful medicine, though dangerous on account of its inflammability, the heat and air contained in the human stomach being sometimes sufficient to set it on fire. The taking such a substance into the body therefore seems not much different from taking actual fire into it; and indeed M. le Roy mentions the case of a woman who had taken only a single grain, and who he says had been recovered, by it, from a putrid fever, but died suddenly from some imprudence. In this woman the whole substance of the body was found luminous upon dissection, and the hands of the operator continued luminous even after being washed. M. le Roy, having taken three grains of this fiery substance, found himself extremely incommoded by it for some hours, and was obliged to drink great quantities of very cold water. Next day he found his muscular powers amazingly increased, and had an almost insupportable venereal irritation. This we see was the consequence of throwing into the body a quantity of heat from without; but if the body itself emits that heat which it invisibly contains, the effects must be the same as though an extraneous quantity had been thrown into it. Neither are we to imagine that the quantity of heat contained in our bodies is small or inconsiderable; for we have already seen that heat consists in the efflux from any substance, of an invisible and most subtile fluid, in all directions. When this flux is gentle, the heat is moderate, but in proportion to the activity of the discharge, the temperature becomes hotter and hotter, and if very violent, the cohesion of the parts is dissolved entirely, and the substance is said to be on fire. There is required therefore only some cause to begin the emission of this fluid; for as soon as this begins, the immense quantity with which we are surrounded, will supply more in abundance,[105] and continue so to do, as long as the original cause subsists, or until the substance can no longer bear the power which operates upon it.