The germ theory has now become so important that it cannot be ignored in a monograph relating to so important an infectious malady as scarlet fever. The relation of microbes to the infectious diseases has been made the subject of investigation by Pasteur, Toussaint, and others in France, and by many in Germany, with most interesting results. The belief held by many, and which seemed very plausible, was that the microbes, instead of sustaining a causative relation to the maladies in which they occur, were the result of these maladies—that they sprang into existence in consequence of the vitiated state of the blood and tissues, just as fungi appear on decaying substances or as the Oidium albicans appears in certain morbid conditions of the buccal surface and secretions. Obviously, in order to elucidate this matter and determine the relation of these parasites to the diseases in which they occur, it was necessary to experiment on animals, but, unfortunately, as a bar to successful experimentation many of the most important infectious maladies which afflict the human race, as typhus and typhoid fevers, the marsh fevers, and syphilis, do not occur in animals, or they occur in a changed and mitigated form. Others, however, can be produced in their typical character in animals, as diphtheria, and others still originate in animals and are transmitted from them to man, as anthrax or splenic fever of the herbivora and hydrophobia. Very interesting and important results have been produced by experimental researches with the microbes of certain of these diseases, which, if applicable to the common and fatal infectious maladies of an analogous nature in man, may yet result in immense benefit in mitigating the virulence of those affections which are the scourge of childhood and which sensibly diminish the increase of population. It has been found possible to cultivate the microbes contained in the blood, tissues, and secretions in certain of the infectious diseases, and after a series of cultivations, so that these organisms are far removed from the animal substance which contained them, and with which they were so intimately associated in the individual, they have been employed for inoculation—with this important result, that the primary disease was reproduced. This seems to indicate beyond question the causative relation of these parasites to the diseases in which they occur. Experiments with the result which I have stated have been made with the microbes of splenic fever, chicken cholera, murrain, and certain other maladies.
Pasteur employs as the media for cultivation—(1st) urine neutralized by a few drops of potash solution; (2d) a liquid prepared by boiling for twenty or thirty minutes the yeast of beer in water, neutralizing, and filtering; and (3d) chicken tea, prepared by boiling equal parts of water and the lean of muscles a quarter of an hour, filtering, and neutralizing. A small drop of infected blood is placed in the liquid of cultivation, and the microbes which it contains multiply so abundantly that the liquid becomes turbid in a short time, and they are found in all parts of it. A drop of this liquid is added to another portion of the medium, and this also soon becomes turbid from the immense development of organisms which have the same microscopic appearance and character as those in the drop of blood. The process is repeated many times, until the microbes are far removed from their original source in the blood and tissues, and a drop of the last cultivation, whether it be the fiftieth or the hundredth, is inserted under the skin of a healthy animal selected for the experiment. If it be true, as stated by the experimenters, that the original disease is thus reproduced with the microbes of at least three or four distinct maladies, this age is distinguished by one of the most important discoveries ever made in pathological studies. It remains to determine whether this great discovery is of general applicability to the infectious diseases with which man is afflicted. If so, it is not improbable that we are on the eve of finding a method by which some at least of these maladies may be prevented or mitigated, as small-pox has been since the time of Jenner. The result of experiments made by Pasteur with the microbes of that fatal malady of the herbivora, known under the various names of splenic fever, anthrax, wool-sorter's disease, and charbon, encourages this belief. Originating among the herbivorous animals, it has in many instances been contracted by individuals who have rapidly perished. Many engaged in assorting alpaca and mohair have lost their lives by it, some with all the symptoms of profound blood-poisoning, without external lesions, and others with redness and swelling at some point of infection where a sore or abrasion existed, but with speedy blood-contamination.
The microbe of this malady, the Bacillus anthracis, occurs in the form of straight filaments with little movement or only with oscillation, and producing bright-shining spores. Now comes a very interesting and important result of experimentation: Pasteur states if several days elapse between the cultivations the virulence of the parasite diminishes, so that he has been able to produce by inoculation with it a mild and never fatal form of charbon, which affords immunity in the animal from any subsequent attack. This opinion was sustained by a trial experiment on sixty sheep. Toussaint and Chauveau claim that they produce a similar attenuation of the virus by defibrinating infected blood, heating it to 55° C. (131° F.) and filtering it. These experiments awaken the hope that the time will come when the acute infectious maladies in man, scarlet fever among others, will be rendered less virulent. That one of them—to wit, small-pox—has for nearly a century been under our control certainly encourages the belief that there is some way to mitigate others of the same class which are equally fatal if not so loathsome.
As yet, observers do not agree in regard to the parasite which is supposed to sustain a causative relation to scarlet fever. Klebs states that it is highly probable that both measles and scarlet fever are produced by micrococci, and he has sketched the design and described the development of a microbe which he designates the Monas scarlatinosum.
The London Medical Times and Gazette for Jan. 28, 1882, contains an account of the supposed discovery of the scarlatinous microbe by Eklund of Stockholm, an authority in the microscopic examination of parasites. He says that scarlet fever is rarely absent from the Swedish capital and from the barracks and dwellings on the isle of Skeppsholm. In the urine of scarlatinous patients he has constantly found a prodigious number of discoid corpuscles, oval or round, their diameter being less than 1/1000 millimetre and from 1/30 to 1/10 that of a red blood-cell. They are colorless or yellowish white, surrounded by a distinct cell-wall, each containing a well-defined nucleus of a deeper hue. Sometimes one or more microbi may be seen. They exhibit rotatory or oscillatory movements, especially observed when a drop of water is added to the fluid. They multiply, as he has frequently seen, by fission—first in the microbes, next in the nucleus, and lastly in the cell-wall. He cannot say whether they develop into a mycelium. At any rate, the development of fine filaments seems to be exceptional. He has never seen them adhere in moniliform chains nor massed as zooglæa. He considers them to be veritable schizomycetes, and proposes the name Plox scindens.
Eklund asserts that he has found these same organisms in vast numbers in the soil- and ground-water of the isle of Skeppsholm, in the mud of the trenches dug for the water-mains, and in the greenish mould upon the walls of the old barracks, where scarlet fever was most rife. He states that scarlet fever has occurred in children after drinking milk mixed with the ground-water of the island, and he observed a case which followed immersion in one of the trenches of the island and the drying of the clothes in a small room. In another instance scarlet fever broke out in a block immediately after exposure of the ground-water by excavations.
It is evident that the discovery of this microbe under such circumstances does not prove that it is the cause of the disease. This can only be determined by inoculation, or by experiments which furnish the conditions of scientific exactness. Although great progress has been made in parasitology during the last decade, it is evident that several years of observation and experimentation must elapse before it is clearly and definitely ascertained whether or to what extent microbes cause scarlet fever and the other exanthematic fevers with which it is classified.
Whether the specific principle of scarlet fever be a micro-organism or a chemical substance, its mode of action and effects have been ascertained by clinical observations. Without doubt it commonly enters the system by the breath, but it may enter in the ingesta, and it infects the blood. That it resides in the blood has been ascertained by inoculation with this liquid, by which scarlet fever has been reproduced in its typical form. From the blood it enters the tissues and secretions. Hence handkerchiefs or linen containing the saliva or mucus of a patient, the epidermic scales shed abundantly in the desquamative period, and probably also the urinary and fecal evacuations, contain the poison, so as to be highly infectious. Even the discharge of a scarlatinous otorrhoea is thought by some to be contagious for a considerable time.
Scarlatina is communicable not only by direct exposure to a patient, but also by exposure to objects which happen to be in his room during his illness, and to which the poison becomes attached, such as clothing, books, and toys; small packages, even letters, it is believed, from cases which have occurred, sometimes convey and disseminate the contagious principle.
In England observations have been made which show that scarlatina has been communicated by infected milk. The disease occurred in the family of a milkman, and the milk, before it was distributed, remained for a time in a kitchen which had been occupied by the patients. This milk was taken by twelve families, and in six of these the disease occurred almost simultaneously at a time when few cases were occurring in the locality. There had been no direct exposure to the carrier of the milk nor to members of the affected family (Taylor). In another instance a woman and her son had scarlet fever while they were serving milk to several families, and the disease appeared in all these families except one, which consisted of old people (Bell). It is known that milk absorbs volatile substances so as to be flavored by them, as is shown in the experiment of placing it in an open vessel in a box with a pineapple; and it may in a similar manner become infected by the specific principle of scarlet fever, or it may be infected by detached particles of epidermis; which is not improbable when one convalescing from scarlet fever is allowed to milk the cows or prepare the milk for distribution.