III Tubercle
Before Laennec, tubercle had been taken for a degenerative change of the tissues, much like other forms of degeneration. It was Laennec who brought men to see that it is a disease of itself, different from anything else; and this great discovery of the specific nature of tubercle, and his invention of the stethoscope, place him almost level with Harvey. He founded the facts of tubercle, and on that foundation Villemin built. In 1865, Villemin communicated to the Académie des Sciences his discovery that tubercle is an infective disease; that he had produced it in rabbits, by inoculating them with tuberculous matter. En voici les preuves, he said. He appealed to these inoculations to prove his teaching:—
La tuberculose est une affection spécifique. Sa cause réside dans un agent inoculable. L’inoculation se fait très-bien de l’homme au lapin. La tuberculose appartient donc à la classe des maladies virulentes.
It was no new thing to say, or to guess, that phthisis was or might be infective. So far back as 1500, Frascatorius had said that phthisis came “by the gliding of the corrupt and noisome humours of the patient into the lungs of a healthy man.” Surely, if clinical experience could suffice, men would have made something out of this wisdom of Frascatorius. They made nothing of it; they waited three hundred years for Villemin to inoculate the rabbits, and then the thing was done—En voici les preuves. Three years later, Chauveau produced the disease in animals, not by inoculation, but by the admixture of tuberculous matter with their food. Then, as the work grew, there came a short period of uncertainty: different species of animals are so widely different in their susceptibility to the disease that the results of further inoculations seemed to go against Villemin; and it was not till 1880 that Cohnheim finally established Villemin’s teaching, and even went beyond it, making inoculation the very proof of tubercle:—
“Everything is tuberculous, that can produce tuberculous disease by inoculation in animals that are susceptible to that disease: and nothing is tuberculous, that cannot do this.”
Then, in 1881, came the welcome news that Koch had discovered the bacillus of tubercle. In his first published account of it (24th March 1882) he says:—
“Henceforth, in our warfare against this fearful scourge of our race, we have to reckon not with a nameless something, but with a definite parasite, whose conditions of life are for the most part already known, and can be further studied.... Before all things, we must shut off the sources of the infection, so far as it is in the power of man to do this.”18
In November 1890 he announced, in the Deutsche Medizinische Wochenschrift, the discovery of tuberculin. Its failure was one of the world’s tragedies. The defeat may not be final, and we may live to see phthisis fought and beaten with its own weapons: but, for the present, it is more to the purpose to consider what other benefits have been gained, from the discovery of the tubercle-bacillus in 1881, in every civilised country in the world.
1. It has given to everybody a more reasonable and hopeful view of phthisis and the diseases allied to it. The older doctrine of heredity, that the child inherits the disease itself, has given way to the doctrine that the inheritance, in the vast majority of cases, is not that of the disease itself, but that of a tendency or increased susceptibility to the disease.
2. It has brought about an immense improvement in the early and accurate diagnosis of all cases. The bacillus found in the sputa, or in the discharges, or in a particle of tissue, is evidence that the case is tuberculous.
3. It has given evidence, which till 1901 was hardly called in question,19 that tabes mesenterica, a tuberculous disease which kills thousands of children every year, is due in many cases to infection from the milk of tuberculous cows. In England alone, in 1895, the number of children who died of this disease was 7389, of whom 3855 were under one year old.
4. It has proved, and has taught everybody to see the proof, that the sputa of phthisical patients are the chief cause of the dissemination of the disease. By insisting on this fact, it has profoundly influenced the nursing and the home-care of phthisical patients; and it has begun to influence public opinion in favour of some sort of notification of the disease, and in favour of enforcing a law against spitting in public places and conveyances. In some of the principal cities of the United States, laws on this subject have already been enacted.
5. It has greatly helped to bring about the present rigorous control of the meat and milk trades. The following paragraph, taken almost at random, will suffice here:—
“Bacteriological examinations during the past year have shown that more milks are tuberculosis-infected than is generally supposed, and the importance of carefully supervising milk supplies is becoming more and more acknowledged. Veterinary surgeons are practically agreed that tuberculin is a reliable and safe test for diagnosing the presence of tuberculosis in animals, but affords no index of the extent or degree of the disease. The test, however, will not produce tuberculosis in healthy animals, and has no deleterious effect upon the general health of the animals. The London County Council have decided that all cows in London cowsheds shall be inspected by a veterinary surgeon regularly once in every three months, and that a systematic bacteriological examination shall be conducted of milks collected from purveyors.” (Medical Annual, 1901.)
6. Tuberculin has come into general use for the detection of tuberculosis in cattle, to “shut off the sources of the infection.” A full account of this method in different countries was given by Professor Bang, of Copenhagen, at the Fourth Congress on Tuberculosis, Paris, 1898. The injection of tuberculin is followed in eight to twelve hours by a well-marked rise of temperature, if the animal be tuberculous. Of this test, Professor McFadyean, Principal of the Royal Veterinary College, London, says:—
“I have no hesitation in saying that, taking full account of its imperfection, tuberculin is the most valuable means of diagnosis in tuberculosis that we possess.... I have most implicit faith in it, when it is used on animals standing in their own premises and undisturbed. It is not reliable when used on animals in a market or slaughter-house. A considerable number of errors at first were found when I examined animals in slaughter-houses after they had been conveyed there by rail, etc. Since that, using it on animals in their own premises, I have found that it is practically infallible. I have notes of one particular case, where twenty-five animals in one dairy were tested, and afterwards all were killed. There was only one animal which did not react, and it was the only animal not found to be tuberculous when killed.”
Two instances of the validity of this test will suffice. In 1899, it was applied to 270 cows on some farms in Lancashire. Of these cows, 180 reacted to the test, 85 did not react, and 5 were doubtful. Tuberculous disease was actually found, when they were killed, in 175 out of the 180 = 97.2 per cent. (Lancet, 5th August 1899.) In 1901, Arloing and Courmont published a critical account of the whole subject, and gave the following facts. In 80 calves, which on examination after death were found not tuberculous, the test was negative: in 70 older cattle, which were tuberculous, the test was positive in every case but one, though the dilution of the serum was 1 in 10.20 It would be easy to add instances of the value of this test, for it is practised far and wide over the world.
7. More recently, the discovery of the “opsonic index,” and its use by Sir Almroth Wright and others, has given a great advance to the observation and treatment of cases of tuberculosis. The administration of the “new tuberculin” is now timed and measured with an accuracy which was absolutely impossible a few years ago.
It is a far cry, from the present method of counting how many tubercle-bacilli are taken up by a single blood-cell, back to Villemin’s rabbits. Every inch of the way, from 1881 onward, the pathological study of every form of tuberculosis, medical or surgical, human or bovine, has been dependent on bacteriology; that is to say, on experiments on animals.