134 ABSTRACTS.

last week of March and the first week of April, and, as elsewhere, the very heavy rainfall in January must be held primarily responsible for the unusual death rate. (" Journal of the Dept. of Agric., Union of S. Africa," Vol. VIIL, April 1924, p. 370.

THE CAUSAL ORGANISM OF FOOT-AND­MOUTH DISEASE.

THE following account of the detection and cultivation of the organism that is the cause of foot-and-mouth disease is abstracted from the Proceedings of the Berlin Microbiological Society at their meetings held on 7th and 19th May 1924.

The work which culminated in the detection of the causal organism was begun by Dahmen and Frosch in April 1923.

In the first attempts to cultivate the organism media which have been used for the cultivation of the virus of contagious pleuro-pneumonia were tried, but without success. A number of other media to which serum, plasma, blood, and various kinds of sugar had been added also failed to yield any growth. In some cases a faint turbidity was produced, but this on investigation was found to be referable to a precipitation of albumen.

The view expressed by Titze that fluid [rom vesicles would be a suitable medium for the cultivation of the virus is not supported by Dahmen, who considers this liquid to be of the nature of a reaction product of the body, its object being the destruction of the virus. Support of this view is furnished by the experiments of Lomer, Frosch, Waldmann, Gins, and others regarding the persistence of the virus in vesicular fluid outside the body.

A method was therefore devised, details of which are to be published later, of separating the virus from the liquid. Artificial cultures were obtained from this virus in liquid and on solid media. Contrary to the observations puplished by Grugel, Titze and Pfeiler, Dahmen, and Frosch failed to obtain any turbidity, or at the most a scarcely perceptible opal­escence in liquid media. The proof of the multiplication of the virus in such media was furnished by subcultivation upon solid media. Up to November 1923 Dahmen succeeded in carrying on the virus on solid media through thirteen generations. Guinea-pigs inoculated with these cultures acquired some degree of immunity as evidenced by the fact that, although they developed primary lesions when inoculated with virulent material from infected animals, they failed to show evidence of any sub­sequent generalised infection, such as was shown by the control animals.

In January 1924 cultures were obtained from another strain of virus. Up to date the first strain (Isle of Reims) has been passed through twenty-five generations, and the second, from the Institute of Infectious Diseases, has reached its seventh generation.

On 17th March inoculations made with the twenty-third and twenty-fifth generations of these two strains yielded exactly the same results as those yielded by the thirteenth generation of the older strain. Cultures were obtained from the lesions produced in the guinea-pigs infected.

The colonies appear under a low magnification as minute points, but they can be recognised without difficulty after incubation for a week. Transplanting cultures offers no difficulty, but it is of the utmost importance that the medium should have an exact composition.

ABSTRACTS. 135

With a culture of the sixth generation Dahmen inoculated a cow by scarification. On the eighth day there was salivation, but no marked rise of temperature. Saliva from this animal was used for the inoculation of a second cow. Aphtha! and salivation were seen on the fourth day. Thus the virulence of the cultures for bovines was established.

Frosch, in introducing the subject of the morphology of the causal organism of foot and mouth disease, said that the work he had done in connection with the causal organism of contagious pleuro·pneumonia was a preliminary training for other more important and possibly more difficult investigations.

The cause offoot and mouth disease, about which much had been written, was the problem to which he next turned his attention. He had not paid much attention to the previous literature because in all cases liquid media only had been used.

It would appear that the cultivation experiments carried out originated in the detection by Frosch, using an ultra-photomicrographic apparatus, of immense numbers of minute rod·shaped structures in filtered fluid from foot and mouth vesicles after dilution with salt solution.

As already stated, cultivation experiments were carried out by Dahmen, who succeeded in obtaining a growth upon solid media. The colonies formed by the organism reach a maximum size of 7 to 8 microns, that is to say, about the size of a red-blood corpuscle, but not infrequently they are only half this size. The cultures are not visible to the naked eye, but colonies can be detected under a low magnification. Under a higher magnification they appear rounded or oval in outline, with an irregularly crenated margin.

Examination with the ultra·microscope shows that the colonies are com­posed of minute rods, a little longer than they are wide, the smallest of which measure less than· I micron. In many places they appear to be in pairs. In size and appearance they agreed exactly with the structures seen in the filtered vesicular fluid.

Photographs of the organism and of the cultures were shown. Dahmen and Frosch suggest the creation of a new genus" Loeffleria" for

this organism, and add the specific name" nevermanni." At the meeting held on 19th May there was a discussion regarding the subjects brought before the meeting of 7th May. The question of the nature of the virus was referred to by some of those present, but it appeared to be the general opinion that the virus of foot-and-mouth disease does not belong to the protozoa. There was some further discussion regarding the claims of Titze and Guth to have been able to cultivate the virus.

In closing the discussion both Dahmen and Frosch spoke. Dahmen pointed out that, while Titze and Guth had produced infection with cultures of the ninth generation, these generations were each only twenty-four hours old. In his own experiments each generation was cultivated for ten days. so that in producing infection with a culture of the sixth genera­tion he was using a virus which had been outside the animal body for sixty days.

In the course of his closing remarks Dahmen described the technique of his method of cultivation. The idea that the vesicular liquid was destructive to the virus was conceived as a result of perusal of the literature regarding d'Herelle's phenomenon.

Otto and Munter have pointed out that the destructive lysin works best at body temperature, and that it has little action at lower temperatures. There is a certain resemblance between this and what has been observed

ABSTRACTS.

in connection with the maintenance of virulence of vesicular fluid from cases of foot-and-mouth disease. Since Dahmen is of the opinion that the liquid from the aphth~ exerts a noxious effect upon the virus, he first attempted to effect a separation of the virus from this liquid. For this purpose he has tried, among other things, animal charcoal, starch, and red blood corpuscles. Fluid mixed with a suspension of starch retained its virulence longer than usual, although separation of the virus from the liquid was not achieved. It appeared to be probable that the virus, which he con­ceived must be corpuscular, could be separated by centrifuging. Fluid from vesicles was diluted with salt solution and centrifuged for half-an-hour, one hour, one and a half hours, and two hours, at 3000 revolutions per minute. A very small amount of sediment was obtained. The supernatant liquid was removed very carefully with capillary pipettes because it was found that the sediment was lost if an attempt was made to decant the liquid. That sedimentation of the virus had been achieved was shown by the fact that while the lower half of the sediment was capable of setting up infection the upper half of the liquid was not. The solid culture medium used is 3 per cent. agar prepared with Martin's broth to which an equal amount of serum (horse or other animal) is added. The reaction of the medium is pH 7'8.

It was not found possible to get primary cultures with the sediment in fluid media, but subcultures from primary growths on the solid medium were readily obtained. Although there is a parallel with d'Herelle's phenomenon, Dahmen states that he does not take it as proved that the noxious substance in the vesicular fluid is a lysin in d'Herelle's sense of the term. The idea, however, formed a working basis from which good results were obtained.

Up to date Dahmen has cultivated six strains from guinea-pigs, two from cattle, and two from pigs.

Frosch in his closing remarks gave reasons for not accepting Stauffacher's view that the cause of foot-and-mouth disease is protozoan in nature. (Ber!. Tier. Wochens., Vol. XL., No. 15, loth April 1924, pp. 186-188, and No 21, 22nd May 1924, pp. 273-275.

RECENT PARASITOLOGICAL DISCOVERIES IN THE CANINE DISTEMPER.

AND PATHOLOGICAL NERVOUS FORM OF

By R. KANTOROWICZ and F. H. LEWY.

FEW diseases have attracted the attention of investigators so much as canine distemper. This is not surprising when the wide distribution, the high mortality, and the extraordinary variation of the symptoms presented are taken into account.

Practically every year some alTeged new specific cause of the disease is discovered, but up to the present definite proofs have been wanting. The truth of this statement is supported by the long list of publications regarding the cause of distemper given by the authors. Methods of treatment are almost as numerous as the symptoms and the alleged causes.

Up to the present little stress has been placed on the course of the disease and the temperature curve. After an initial period of three to seven days the disease sets in with a high fever. This may last for a few hours only, a moderate degree of fever lasting for two to five days, or there