The result of this clumping is also plainly visible to the naked eye, by the subsidence of the agglutinated bacteria to the bottom of the containing vessel: and thus an easy practical mode of diagnosis is afforded by it.
As with typhoid, so with Malta fever, cholera, and some other infective diseases. And the unimaginable fineness of this reaction goes far beyond the time of the disease. Months, even years, after recovery from typhoid, a fiftieth part of a drop of the blood will still give Widal's reaction: and it has been obtained in an infant whose mother had typhoid before it was born. A drop of dried blood, from a case suspected to be typhoid, may be sent a hundred miles by post to be tested; and typhoid, like diphtheria, may now be submitted to the judgment of an expert far away, and the answer telegraphed back. It would be difficult to exaggerate the practical importance of this reaction for the early diagnosis of cases of typhoid fever, especially those cases that appear, at the onset, not severe.
Malta Fever
The specific organism of Malta fever (Mediterranean fever), the bacillus Melitensis, was discovered in 1887 by Surgeon-Major David Bruce, of the Army Medical Staff. Its nature and action were proved by the inoculation of monkeys. The use of Widal's reaction is of great value in this disease:—
"The diagnosis of Malta fever from typhoid is, of course, a highly important practical matter. It is exceedingly difficult in the early stages." (Manson, loc. cit.)
As with typhoid, so with Malta fever, Netley led the way to the discovery of an immunising serum. In the course of the work, one of the discoverers was by accident infected with the disease:—
"He was indisposed when he went to Maidstone to undertake anti-typhoid vaccination, and after fighting against his illness for some days, he was obliged to return to Netley on 9th October. Examination of blood-serum (Widal's reaction) showed that he was suffering from Malta fever. It appears that he had scratched his hand with a hypodermic needle on 17th September, when immunising a horse for the preparation of serum-protective against Malta fever; and his blood, when examined, had a typical reaction on the micrococcus of Malta fever in 1000-fold dilution. The horse, which has been immunised for Malta fever for the last eight months, was immediately bled, and we are informed that the patient has now had two injections, each of 30 cub. cm. of the serum. He is doing well, and it is hoped that the attack has been cut short." (British Medical Journal, 16th October 1897.)
About fifty cases had up to September 1899 been treated at Netley "with marked benefit: whereas they found that all drug-treatment failed, the antitoxin treatment had been generally successful."[36] A good instance of the value of the serum-treatment of Malta fever is published in the Lancet, 15th April 1899. For a later account of this treatment and of its efficacy, see the Philadelphia Medical Journal, 24th November 1900.
Another point is noted by Sir Patrick Manson, in his recent Lane Lectures (Constable, 1905). "For some time back," he says, "a commission of experts, working under the direction of the Royal Society, has been studying this disease in Malta. The commission has accumulated much detailed information; but the most important observation it has published is the fact that a large percentage of the goats in Malta are infected with Micrococcus melitensis, and that the milk of the infected goats contains the bacterium. May not this account for the great prevalence of Mediterranean fever there and in other places having perhaps a similar milk-supply?"