Yet the germ-theorists have not left us entirely without hope. One of Pasteur’s most distinguished pupils, M. Metschnikoff, offers us salvation through faith in his phagocytes. The white blood corpuscles are for ever on the watch for the incursions of disease germs. These they instantly arrest and imprison by taking them into their own substance, digesting and converting them to their own uses. Whenever there is an extra demand for the services of these admirable blood-police, a large number are attracted to the point where the burglarious and murderous enemy has entrenched himself; and if the system is in a position to maintain a sufficient force of these guardians of health, the enemy is rapidly digested, and the effete products are expelled by the regular physiological channels.
It has been found that men and animals may be insusceptible to an infective disease by natural immunity. Not all persons subjected to exposure to epidemic diseases contract them. Ordinary sheep readily succumb to anthrax, but Algerian sheep resist any but large doses of the virus.[1051] Acquired immunity is that by which one attack, say of measles or of small-pox, protects against a second. Acclimatization also affords immunity. Pasteur, in his researches on fowl cholera, noticed that in non-fatal cases the disease did not recur. This set him to work out a theory of attenuated inoculations which should afford protection by giving the disease in a mild form in cultivations of the micro-organism. Pasteur next endeavoured to protect animals against anthrax by inoculating them with a mitigated virus. His results were criticised and his researches opposed by Koch, who came to the conclusion that the process did not admit of practical application, chiefly because the immunity would only last a year, and on account of the danger of disseminating a vaccine of the necessary strength.[1052] The theory of protective inoculation in hydrophobia has been much discussed. Pasteur’s explanation does not entirely satisfy some experts. Dr. Sims Woodhead gives the following: “I am inclined to think that the explanation advanced by Wood and myself, that the treatment consists essentially in causing the tissues to acquire a tolerance before the microbe has had time to develop, is more in accordance with the facts. The tissue cells are acted upon by increasingly active virus, each step of which acclimatizes the cells for the next stronger virus, until at length, when the virus formed by the micro-organisms introduced at the time of the bite comes to exert its action, the tissues have been so far altered or acclimatized that they can continue their work undisturbed in its presence; and treating the micro-organisms themselves as foreign bodies, destroy them. When the cells are suddenly attacked by a strong dose of the poison of this virus, they are so paralysed that the micro-organisms can continue to carry on their poison-manufacturing process without let or hindrance; but when the cells are gradually, though rapidly, accustomed to the presence of the poison by the exhibition of constantly increasing doses, they can carry on their scavenging work even in its presence, and the micro-organisms are destroyed, possibly even before they can exert their full poison-manufacturing powers.”[1053]
Ptomaines.
The germ theory has thrown great light upon the subject of certain mysterious organic poisoning processes, which long puzzled analysts and physicians. Diseased meat, fish, cheese, and other articles of food frequently cause symptoms of poisoning in those who have partaken of them. The analyst failed to detect the precise agent which caused the mischief, and it was not till the bacteriologists investigated the subject that it was satisfactorily explained. In 1814, Burrows described a poisonous substance in decaying fish. In 1820, Kerner described a poisonous alkaloid which he discovered in sausages. In 1856, Panum isolated a poison from some decomposing animal matter. Zuelza and Sonnenschein from the same substance obtained a poison which closely resembled atropine in its physiological action. Selmi between 1871 and 1880 described substances which he called cadaveric alkaloids or ptomaines. Pasteur and others, working in the same direction, have greatly advanced our knowledge of these deadly agents. Bacteria are now known to have the power to build up deadly substances as they grow in dead or living animal tissues, just as plants build up poisons in their own tissues; these substances exert a deadly influence on the nerve centres, and hence a cheese bacillus may be as dangerous to human life as a dose of aconite.
Lister’s Antiseptic Surgery.
What is commonly known as “Listerism” is a development of the germ theory of disease, which has revolutionised the art of surgery by its direct and indirect influence. Pus formation, the result of destructive processes which prevent the healing of wounds, was discovered to be due to the action of germs falling from the atmosphere on the injured flesh. Lister sought to destroy these germs by powerful disinfectants. This was the first step in the antiseptic treatment. When carbolic-acid lotions were applied for this purpose, Lister discovered that the wound healed rapidly. He believed that he had destroyed the micro-organisms by the carbolic-acid lotions. But Lister improved on this process, and seeing how difficult it is to destroy the germs when they have once entered the tissues, he invented a method whereby they were prevented from gaining admission at all. He fought the micro-organisms in the atmosphere of the operating room, in the dressings, instruments, and hands of the operator, and thus gradually built up his system of absolute surgical cleanliness called antiseptic surgery. Even those surgeons who rejected his method in its entirety, and declined to adopt his complicated system of dressings, devoted so much attention to the minutest cleanliness, that they achieved results not less successful than those of the inventor of the antiseptic system itself.
Sanitary Science.
Hygiene, the art of preserving health, has always been recognised as a branch of medical science, not less important than that which concerns itself with the cure of disease. Moses (B.C. 1490) enjoined the strictest cleanliness, and anticipated our modern sanitary laws. Hippocrates embodied in his works treatises on hygiene, which existed in Greece probably long anterior to his time. The value of attention to rules of diet and exercise was recognised by Herodicus, one of his preceptors, who introduced a system of medicinal gymnastics for the improvement of the health and the cure of disease. Such rules must to a greater or less extent have always been in force in any well-constituted army. Gymnasts, athletes, and others must have been fully aware of the necessity for attending to such rules. Hippocrates, in his treatise Airs, Waters, and Places, has insisted on the duty of the physician to study the effects of the seasons, the winds, the position of cities, and the diseases which are endemic and epidemic in them, the qualities of waters, and their effects on public health, and so forth. Had men taken up the study of Hygiene where Hippocrates left off, we should not have heard of the plagues, pestilences, and epidemics which up to modern times periodically devastated the civilized world.
Hygiene.
Mr. Parkes, in the introduction to his Manual of Practical Hygiene, defines hygiene in its largest sense to signify “rules for perfect culture of mind and body.” The two are not to be dissociated. Every mental and moral action influences the body; the physical conditions equally re-act upon the mind. He admirably says: “For a perfect system of hygiene we must combine the knowledge of the physician, the schoolmaster, and the priest, and must train the body, the intellect, and the moral soul in a perfect and balanced order. Then, if our knowledge were exact, and our means of application adequate, we should see the human being in his perfect beauty, as Providence, perhaps, intended him to be; in the harmonious proportion and complete balance of all parts in which he came out of his Maker’s hands, in whose divine image, we are told, he was in the beginning made.” Mr. Parkes asks if such a system is possible? He replies that we can even now literally choose between health and disease. There are certain hereditary conditions which we may not be able to avoid, and men may hinder our acquisition of the boon; but as a race man holds his own destiny in his hands, and can choose the good and reject the evil. Exit the disease-demon! Fevers and other epidemic diseases are no longer attributed to the anger of the Supreme Being; they may be prevented. If we use the words scourge, plague, visitation, and the like, it is merely because we recognise that Nature can take offence at our violation of her laws, and visit us with the penalty.