ABSTRACTS.

IMMUNITY AGAINST TUBERCULOSIS IN CATTLE.

IN a previous paper the authors showed that immunity to, or rather tolerance of, infection with tuberculosis in cattle appears to be due to the antecedent presence of tubercle bacilli within the system, and that the tolerance is closely related to the nature of the bacilli us~d. The question has arisen as to what part the component elements of the bacillus, the lipoids, the tuberculins, and the bacillary protoplasm may play respectively in the pro­duction of this immunity.

Tile Effects produced by the Ltpoids.-The lipoids used were extracted from bovine tubercle bacilli first with boiling acetone and then with boiling benzene. They were then melted together and washed with boiling water for two hours, in order to remove the greater part of the substances soluble in water, and in particular any traces of tuberculin. The last traces of water were removed by again dissolving the lipoids.

Two experiments were carried out with the lipoids thus obtained. Two calves, aged respectively two and eight months, were inoculated at an interval of ten days intravenously with 100 and 200 mg. of the lipoids emulsified by means of ox bile. A month later they were inoculated intravenously with 3 mg. of bovine tubercle bacilli. Death with advanced tuberculous lesions took place in twenty-four and twenty-seven days respectively.

The lipoids therefore appear to play no part in the production of immunity. The Effects produced by TubercuHn.-Two experiments have also been

carried out in this connection-one with crude tuberculin prepared from bovine tubercle bacilli, and the other with the same tuberculin precipitated with alcohol. In the former instance two intravenous injections of 10 cc. of crude tuberculin were given at an interval of ten days, and in the latter 20 and 50 cg. of precipitated tuberculin were given at the same interval. In both cases an intravenous test inoculation of 3 mg. of bovine tubercle bacilli was given a month later. One animal was killed when in extremis on the fifty-eighth day, and the other died on the fifty-seventh day. Both were affected with acute rapidly progressive tuberculosis.

From these experiments it appears that injections of tuberculin, either crude or precipitated, have the effect of sensibly retarding the development of the tuberculosis produced by the test inoculations.

The Effect of Entz're BadlH killed by Heat and Washed.--Although experi­ments of this nature would not yield any positive evidence as to the value of the bacillary protoplasm, owing to the bacilli having been heated and to the fact that the most careful washing cannot be relied upon to remove the last traces of tuberculin, the authors thought it well to carry out an experi­ment in order to ascertain whether the slight protective power attributed to dead bacilli by various authors depends upon the tuberculin enclosed within the bodies of the bacilli, the tuberculin thus enclosed possibly acting with greater certainty than large doses of solution introduced into the vascular system.

An eight-months-old calf was inoculated intravenously with 20 mg. of bacilli heated for thirty-six minutes at 65° C. and then washed with salt solution. Three months later the animal was tested with tuberculin and gave a very pronounced reaction. It was slaughtered on the same day, and

ABSTRACTS;

at the post-mortem the lesions of chronic, slowly progressive tuberculosis were found.

The Effect oj the Bacillary Protoplasm.-To elucidate the part played by the protoplasm of the bacilli it was necessary to use bacilli which had neither been heated nor treated with antiseptics, and in which the tuberculin was destroyed as fast as it was produced by the culture medium itself, so that the bacilli could not carry any of it away with them. The author's strain of bovine bacilli cultivated through seventy passages upon glycerinated ox bile fulfilled these conditions.

Cultures upon this medium are very fragile and die within a maximum period of two months. The medium upon which the bacilli have grown is shown to contain no tuberculin, because it will not cause a reaction when injected in doses of 5 cc. subcutaneously into tuberculous animals.

The question arises whether the absence of tuberculin in cultures grown upon media containing bile is due simply to an action of the bile upon the tuberculin or to an actual modification of the bacillus itself produced by the medium.

Details are given of experiments showing that when the same strain of bovine bacilli is transferred back to a medium containing no bile a tuber­culin capable of producing reaction results, but it has also been found that the attenuation of the virulence persists in such media.

On these grounds, therefore, the authors are of the opinion that the bacilli used to test the immunising power of the bacillary protoplasm fulfilled the conditions laid down.

An eight-months-old calf was inoculated intravenously with 100 mg. of the seventieth generation of hacilli grown upon the bile medium. The culture was six months old and was dead. It also contained no tuberculin. A month later 3 mg. of virulent culture were administered intravenously. The animal died on the twenty·eighth day, and extensive pulmonary tuber­culosis was found at the post-mortem examination.

It may be supposed that the absence of protective power on the part of the bacillary protoplasm may be due to the fact that the bacilli are not absorbed into the system, and, as the protoplasm carries no tuberculin with it, this latter confers no relative degree of tolerance comparable to that ohtained as a result of an inoculation with tuberculin alone.

The accuracy of this hypothesis is demonstrated by an experiment of which the details are given, and it also shows that the addition of Koch's tuberculin to the protoplasm is insufficient to confer a durable immunity upon an animal.

An eight-months-old calf was inoculated intravenously with 100 mg. of bacilli of the seventieth generation grown upon bile medium which were triturated in a mortar with z cc. of crude tuberculin and incubated for twenty-four hours. A month later an intravenous test inoculation of 3 mg. of bacilli wa~ given. Di!ath took place on the fifty-fourth day, and the animal was found to be affected with acute tuberculosis.

Protective Action exercz'sed by Living BaciIH.-In this connection the authors recapitulate a number of experiments which have been previously published, but which may be summarised here as follows :-

Eight calves were inoculated intravenously at an interval of a month with I and 5 mg. of bovine hacilli grown upon bile medium. A month later the whole batch, together with a control calf of the same age, were inoculated intravenously with 3 mI!'. of virulent bovine bacilli.

The control animal died of tuberculosis on the thirty-fourth day. The vaccinated animals were killed at intervals of one to eighteen months.

All were found to be free from visible tuberculous lesions, but material taken

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from the .bronchial glands of each was proved to contain living virulent bacilli by the inoculation of guinea-pigs.

These experiments show that the tolerance of bovine a:J.imals to infection with tuberculosis is dependent upon the presence in their systems of living tubercle bacilli.

The following conclusions are drawn :-1. The lipoids soluble in boiling acetone and benzene extracted from

tubercle bacilli exercise no protective action. 2. Crude or precipitated tuberculins, such as are usually prepared ID

laboratories, exercise an obvious effect, which is merely a slowing of the process of development of the disease.

3. Bacilli killed by heat derived from ordinary glycerinised culmre media possess a slight protective power, due to the small amount of tuberculin

·carried aloug with them or contained in their bodies. 4. The intact bacillary protoplasm obtained from dead bacilli which are

devoid of tuberculin possesses no immunising action at all. s. Lasting tolerance possessed by bovines to infection with tuberculosis

-is due to the presence in their systems of living bacilli. The saprophytic existence of tubercle bacilli in the system leads to the production of soluble immunising substances different from those obtained in artificial culture media. (Calmette and Guerin, Ann. Ins!. Past., Vol. XXVIII., NO.4, April 1914, pp. 319-337.)

THE INTRAPALPEBRAL AND INTRADERMIC PALPEBRAL TUBERCULIN TESTS.

THE author discusses at some length the objections that may be raised to the ·use of the subcutaneous tuberculin test, dividing these objections into those which concern the practitioner and those which concern the owner.

The principal objections encountered by the practitioner are: The amount ·of trouble involved in taking the temperatures; the possibility of errors being made in reading the temperatures; the difficulty of interpreting irregular results; the necessity of keeping the animals indoors, which is in itself sometimes sufficient to cause.a rise of temperature; the impossibility of applying the test to animals in a febrile condition; the necessity of carrying out the test at certain hours at the risk of makIng serious errors.

These objections are not objections to the method Itself, but are due to the conditions under which the test has to be carried out.

As regards the objections that may be raised by the owners of cattle, the author poinls out that there may be a reduction In the secretion of milk in reacting animals. There is a danger of specific mastitis occurring after .a longer or shorter interval, and, finally, there is the danger of aggravating the general condition of diseased animals

In view of these objections the author is convinced that the local tests, intradermic and intrapalpebral, are more useful, more practical, and more economical from the owner's point of view, and from the practitioner's point of view more remunerative than the old method of subcutaneous injection.

The difficulty of applying the test is imaginary, provided a suitable syringe is used; this should have a capacity of I ccm. The needle should be

.about If cm. in length and '7 mm. in diameter. The barrel of the syrmge should be graduated into tenths, and the piston. rod should have a travelling ,stop on it.