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Lhoek dream when, more than two hundred SOME POISONS AND THEIR

PREVENTION ITTLE did the learned Dutchman Leeuwenyears ago, he recorded, in his Arcana Naturæ, that he had found "viva animalcula” in his saliva, that this, the first beginning of bacteriology, would lead, a couple of centuries later, to the inauguration of a new era in the treatment of disease, in which these so-called animalcula, from being considered as curiosities, would come to be regarded as powers for good and evil of the first importance. Protective inoculation or serum theraphy, of which the public have lately heard so much in connection with diphtheria, is the direct outcome of bacterial investigations which during the last two decades have been pursued with such zeal in every part of the globe.

The vast domain of immunity, which until recently was an undiscovered country, is now being bit by bit annexed, and in all directions workers

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are engaged upon opening up new tracts, in overcoming difficulties, in changing chaos into order.

The problems which surround immunity are of so complex and subtle a character that their mastery is by no means either easy or rapid, and many recondite researches appear at frequent intervals on this subject in foreign and other scientific journals, rendering it a difficult matter to keep pace with the new discoveries and the latest theories.

The interest in this country in toxins and antitoxins not unnaturally centres round that branch of the subject which deals with diphtheria, this disease having of late years figured so prominently in our mortality tables, whilst the production of diphtheria and other anti-toxic serums has been so finely elaborated abroad that it already constitutes an article of commerce, and doubtless helps to swell the exports of our great continental commercial rival.

In this connection the following statistics, published by Dr. Jalzer, of the Mülhaus Hospital, are of interest regarding the mortality from diphtheria before and after the introduction and application of diphtheria anti-toxin. The deathrate from this disease, writes Dr. Jalzer, which in 1892 and 1893 was fully 50 per cent., fell in 1895

to 38.5 per cent., in 1896 to 28.8 per cent., in 1897 to 16 per cent., to 20 per cent. in 1898, 15:15 per cent. in 1899, and 18.75 per cent, in 1900.

So far the efforts which have been made to mitigate human suffering have attracted most attention; but it will be remembered that Pasteur, before he commenced the study of hydrophobia, had already won his laurels in combating disease in the victory he gained over anthrax, the ravages of which so frequently decimated the herds of the French farmer and robbed him of his well-earned return on his capital and labour.

In summoning the brilliant Director of the German Imperial Board of Health to South Africa to investigate the nature of rinderpest, and, if possible, discover a means of protecting cattle from its onslaught, the Cape Government afforded another opportunity for the scientific study of a disease associated with animals, upon the successful mastery and limitation of which the agricultural prosperity of South Africa is so largely dependent, being as it is one of the most fatal and contagious maladies to which cattle are subject. Apart from the great commercial importance attending Dr. Koch's discovery of a device whereby cattle can be immunised or protected from contracting rinderpest when exposed to its contagion, this discovery is of great scientific interest, inasmuch

as it has inaugurated a new departure in methods of immunisation.

The previous methods in vogue for inducing immunity in animals from a particular disease consisted in converting the virus itself into a vaccine, as was done by Pasteur in his classical investigations on anthrax and its prevention; and secondly, the employment of anti-toxic serums, in which the virus is not directly inoculated into the animal to be protected, but in which an intermediary is employed between the virus and its victim. This intermediary, or living machine for the generation of the anti-toxin, is usually a horse, which is artificially trained by being given gradually increasing doses of the virus or toxin, until it ultimately withstands doses which in the first instance would infallibly have killed it. When the animal has arrived at this satisfactory stage or condition of complete immunity, some of its blood is from time to time drawn off, and the serum thus obtained constitutes the anti-toxin which now figures so prominently in modern therapeutics. Besides diphtheria-antitoxic serum there are also those of tetanus, or lock-jaw, plague, the famous anti-venene serum, about the discovery and preparation of which greater detail is given later on, and many others which are still the subject of experimental inquiry.

Now Koch's method for the compassing of rinderpest differed from both the systems above mentioned, inasmuch as he neither employed artificially weakened cultures of the virus, or an anti-toxic rinderpest-serum; instead he took one of the natural secretions of an animal infected with rinderpest, and by injecting this into a healthy animal it was discovered that the latter, as is the case with a vaccine, suffered only local and temporary discomfort, and acquired pronounced immunity from the active virus. The secretion selected by Dr. Koch and his assistant, Dr. Kolle, for this purpose was the gall, and it might be supposed, from the fact that its inoculation into healthy animals did not communicate the disease, that the rinderpest bacteria were absent from the gall. But this is not so, for Dr. Kolle has succeeded in isolating the latter from the gall of infected animals, and, moreover, has proved them on isolation to possess their full complement of virulence. Further investigations made by Koch and Kolle have shown that the explanation of this seeming anomaly is to be found in the fact that the gall of an animal suffering from rinderpest contains a substance which prevents the migration of the rinderpest bacteria, with which it is associated, from the point of inoculation. Hampered in their movements by the controlling

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