lu some, signs of post-mortem digestion were found

rabies, and in one instance from that of a man who bad died with hydrophobia.

Four sériés of experiments of observations in which rabbits were bitten by rabid dogs from the streets were made. In one of thern the dog by which the rabbit was bitten exhibited the dumb form, in others the furious form, of the disease. In each sériés excepting the first a large proportion of the rabbits died; the symptoms presenting themselves in these cases were identical with those observecl in the rabbits inoculated from M. Pasteur’s virus, but the duration of the symptoms was usually longer. As lias been stated, rabbits inoculated by M. Pasteur’s virus rarely show symptoms during more than three days before death, whereas the rabbits bitten by rabid dogs from the streets olten livc for a week after the appearance of the first symptoms.

The post-mortem appearances in the rabbits dying after having been bitten by rabid dogs of the streets were the same as those alreadv clescribed in rabbits inoculated with the virus from M. Pasteur’s rabbits.

In the case of rabbits inoculated by trephining with the virus from animais dying of rabies of the streets, the incubation periocl was from 14 to 21 days. In ail cases the symptoms were similar to those produced by M. Pasteur s virus, and those of rabbits bitten by rabid dogs from the streets ; butin the prolongation of the disease approached more closely in character to the. latter.

The results of these experiments confirai several of the chief observations made by M. Pasteur; especially —

1. — That the virus of rabies may certainly be obtainecl from the spinal cords of rabbits and other animais that hâve died of that disease.

2. — That, thus obtained, the virus may be transmitted by inoculation through a succession of animais, without any essential alteration in the nature, though there may be sonie modifications of the form, of the disease produced by it.

3. — That, in transmission through rabbits, the disease is rendered more intense; both the period of incubation, and the duration of life after the appearance of symptoms of infection, being shortened.

4. — That, in different cases, the disease may be manifestée! either in the form called dumb or paralytic rabies which is usual in rabbits; or in the furious form usual in dogs; or in forais intermediate between, or combining, both of these, but that in ail itis true rabies.

5. — That the period of incubation and the intensity of the symptoms may vary according to the method in wich the virus is introduced, the âge and strength of the animal, and some other circumstances ; but, however variable in its intensity, the essential characters of the disease are still maintained.

The certainty that the virus of rabies can thus be transmitted without essential change made it désirable, in the next place, to ascertain whether, as M. Pasteur States, it can be so attenuated that it may be inoculated without risk to life, and whether animais thus inoculated are thus made safe from rabies. The methods for tliis protectivc inoculation which M. Pasteur lias employed are described.

lo test them, six dogs were “ protected by injecting subcutaneously the émulsions of spinal cords of rabbits which had died of rabies; beginning

MALADIES VIRULENTES

with that of a cord which had been dried for 14 days, and, on each following clay, using that of a cord which had been dried for one day less, till at last that from a fresh cord was used.

None of these dogs suffered from the injections; and when they were completed, the six dogs thus “ protected ”, and two others nnprotected, and some rabhits nnprotected, were made insensible with ether, and were then hitten by rabid dogs, or hy a rabid cat, on an exposed part.

A “ protected ’ dog, No. 1, was bitten on July 8, 1886, by a dog which was paralytically rabid. lt remains perfectly well.

An “ unprotected dog, No. 1, was bitten a few minutes afterwards by the same rabid dog, and died paralytically rabid.

A “ protected ” dog, No. 2, was bitten on November 6, 1886, by a dog which was furiously rabid; it remains well. At the same time four “ unprotected ” rabbits were bitten by the same rabid dog, and of these two died of rabies in the usual form ( i.e . 50 per cent, of animais bitten).

The same results followed with the ££ protected dog) No. 3, and the “ unprotected ” rabbits, bitten at the same time. The dog still lives, the rabbits died of rabies.

The “ protected ” dogs, Nos. 4 and 5, were bitten on January 20, 1887, by a furiously rabid dog; and on the same day the ££ unprotected ” dog, No. 2, and three ££ unprotected ” rabbits were bitten by the same dog. The ££ protected ” dogs remain well; the ££ unprotected ” dog and two rabbits died with rabies (i.e. 75 per cent, of the animais bitten.)

The ££ protected ” dog, No. 6, was bitten on three different occasions by a furiously rabid cat on September 7, 1886; by a furiously rabid dog on October 7, 1886 ; and by another furious rabid dog on November 6, 1886. It died ten weeks after being bitten for the third time, but not of rabies. It had been suffering with diffuse eczema during the wholc of the time that it was under observation, and it died of this. At the post-mortem examination, no indication of rabies was found; and two rabbits, inoculated by trephining with the crushed spinal cord, showed no sign of rabies, either during life or, when they were killed several months afterwards, in any appearance after deatli. It was thus made certain that the dog was not rabid.

Thus, ail the experiments performed by Mr Horsley bave confîrmed those of M. Pasteur, and the experiments last described hâve shown that animais may be protected from rabies by inoculations with material derived from spinal cords prepared after M. Pasteur’s method. The protection may be deemed somewhat similar to that given by the inoculation for anthrax, or by vaccination for small-pox, though the theory of the method of inoculation devised by M. Pasteur is very different from that upon which vaccination for small-pox and inoculation for anthrax is based. The further step, the prévention of rabies or hydrophobia in animais or in persons into whom the virus lias already been introduced by liites or otherwise, is considered in the body of the Report.

In the course of his experiments, Mr Ilorslcy observée! many interesting facts concerning the modification of the action of the virus according to the method of its inoculation, and the condition of the animal inoculated; but lie

MALADIES VIRULENTES

fourni nothing to justifia belief that any animal not inoculated is insusceptible of rabies, or that the disease ever avises spontaneously (*).

Coincidently with these experiments, some were made by Mr Dowdeswell for the purpose of ascertaining whether any drugs can protect an animal from rabies. Their resuit is recorded in a paper read before the Royal Society, and may bc summed up in the statement that rabies can neither be prevented nor influenced in its course, unless it be for the worse, by any of the drugs that were employed, including allyl alcohol, atropine, benzoate of soda, chloral, cocaine, curare, iodine (dissolved in iodide of potassium), mercuric perchloride, quinine, saiol, strychnine, uretliane.

M. Pasteur’ s Methods of Préventive Inoculation (2).

M. Pasteur believes that the virus of rabies is a living micro-organism, and that, like some others, it produces in the tissues it invades an excretory substance by wbich, when présent in sufficient quantity, its own development and increase are checked, as are those of the yeast ferment by the alcohol produced in the vinous fermentation. In accordance with this theory, he thinks that the spinal cords of animais that hâve died of rabies contain both the virus and this excretory substance which, practically, may be deemed its antidote. He believes therefore that by injections of an émulsion from sucli spinal cords into the Systems of animais bitten or inoculated with the virus of rabies, the antidote may be able, duringthe period of incubation, to arrest and prevent the fatal influence of the virus. But, in order to avoid the possibility of injecting a still potent virus, M. Pasteur holds that the virus in the spinal cord must be weakened by drying the cord in a pure and dry atmosphère at a température of 20° C. ; in which drying the efficieney of the antidote may be reduced to a mucb less extent than the potency of the virus. By such drying this potency may be so reduced that an émulsion of the dried spinal cord may be injected without any risk of producing rabies : and this risk is in no measure increased by the daily injections of émulsions from cords dried during a gradually less number of days, and which, though more virulent than those hrst used, still contain a larger proportion of the antidote than of the virus.

In accordance with this theory, the method of the préventive injections first used by M. Pasteur was adjusted in the following manner : —

DAYS OF INOCULATION

Ist.

2nd.

3rd.

4th.

5th.

6th.

7th.

8tii.

9th.

ÎÜTII.

Days during which the spinal cord had been dried.

1. The minuter tacts connected with ali these experiments will soon be communicated to one of the scientific Societies.

2. As derived from the observations made by the Committee, and from a fuit description supplied by Prof. Dr. Grancher, April 11, 1887. — Deuxième appendice au « Report ». Nature, XXXVI, 7 juillet 1887, p. 236-237.

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In conséquence of some deaths among those who had been thus treated, M. Pasteur deemed it necessary, in cases of very severe lûtes and of persons bitten long before the treatment could be commenced, to increase tbe intensity of the treatment by more speedily increasing the strengh of the injections, by more frequent répétitions of them, and by using on certain days spmal cords dried during only three, two, and one days. Thus in September and October 1886 he adopted the following formula

DAYS OF INOCULATION

lST.

2nd.

3rd.

4th.

5th.

Days’ drying of the cords.

DAYS OF INOCULATION

6th.

7th.

8th.

9th.

IOth.

Hth.

Days’ drying of the cords.

In very severe and perilous cases this course was repeated even three or four times. It was distinguished as the méthode intensive, and among su ch severe cases it was followed by a marked diminution of mortality. But when it appeared possible that it might be dangerous, M. Pasteur changed it for that which he now uses, and which may be thus represented :

DAYS OF INOCULATION

lST.

2nd.

3bd.

4th.

5th.

6th.

7th.

Days’ drying of the cords .

DAYS OF INOCULATION

8th.

9th.

IOth.

IIth.

12th.

13th.

14th.

15tii.

Day’s drying of the cords .

The material for injection is prepared by crushing portions of the dried spinal cord, and diffusing them in sterilized broth free from ail risk of putréfaction, décomposition, or any change due to the presence of other microorganisms; and the injection is made with syringes through fine tubular needles into the sub-cutaneous tissue.

For transmissions of rabies through rabbits, in order to obtain the spinal cords required for its prévention in other animais, injections of virus of highest intensity are made through minute holes in the skull into the space under the dura mater or fîbrous coverino' of the brain.

The materials for the protective inoculations are prepared in the saine manner as those for the préventive, from spinal cords dried from ten days to one day.