Other results, in addition to this one, were not slow in revealing themselves. It was established that not only the brain, but the spinal marrow, along its whole length, may be rabic, and that the nerves themselves throughout their whole system, from the centre to the periphery, may contain the virus of hydrophobia. If there exists a microbe of hydrophobia, its medium of cultivation in the body is, par excellence, the brain, the spinal marrow, and the nerves. It was also established that there were localisations of virus in certain parts of the mucous system, and that the very considerable differences of rabic symptoms which exist in different cases of hydrophobia, must be sought for in this fact. At the moment of death the medulla oblongata is always rabic. Finally, it was established that hydrophobia could be given (and almost as rapidly as by trepanning) by inoculating rabic nervous matter into the circulation of the blood by a vein.
In presence of such facts it is easy to account for what takes place in the case of a bite from a mad dog. The circulation of the blood carries the virus to the surface of the brain, or to the surface of the spinal marrow; there it houses itself in particular spots, and, little by little, invades the nervous matter. This last would be progressively attacked throughout, if death from the medulla oblongata did not almost always supervene before the propagation of the virus can become general.
The saliva glands are often rabic, doubtless because the virus oozes into them, little by little, from the nerves which enter these glands. Thus may the presence of this virus be explained in the saliva of mad dogs, where, at all times since the disease was first known, it has been found to exist. When the first point attacked by the virus is the spinal marrow, or certain portions of it, a general paralysis often precedes death. In this case the howling and biting symptoms are for the most part absent, and the dog continues to be caressing until it dies.
In a thesis written by M. Roux, Pasteur's laboratory assistant, last July, we read the following:—'If we examine with care a little of the pulp taken freshly from the brain of a rabid animal, and compare it with the same substance from the brain of a healthy animal, it is difficult to distinguish any difference between the two. In the rabic pulp, however, besides the granulations which are found in profusion in the healthy pulp, there seem to exist little grains of extreme minuteness, almost imperceptible even with the strongest microscopes. In the cephalo-rachidic liquid so limpid in appearance, it is possible with great attention to detect similar little grains. Can this be the microbe of hydrophobia? Some do not hesitate to affirm that it is. For ourselves, as long as the cultivation of the microbe outside of the organism has not been effected, and that hydrophobia has not been communicated by means of artificial cultures, we shall abstain from expressing a definite opinion on the subject.'
But the grand problem in regard to hydrophobia is, not so much the isolation of the microbe, as the finding of a means of preventing this frightful disease.
Even now the experiments are in full swing. Biting dogs and bitten dogs fill the laboratory. Without reckoning the hundreds of mad dogs that have died in the laboratory during the last three years, there never occurs a case of hydrophobia in Paris of which Pasteur is not informed. Not long ago a veterinary surgeon telegraphed to him, 'Attack at its height in poodle-dog and bull-dog. Come.' Pasteur invited me to accompany him, and we started, carrying six rabbits with us in a basket. The two dogs were rabid to the last degree. The bull dog especially, an enormous creature, howled and foamed in its cage. A bar of iron was held out to him: he threw himself upon it, and there was great difficulty in drawing it away from his bloody fangs. One of the rabbits was then brought near to the cage, and its drooping ear was allowed to pass through the bars. But, notwithstanding this provocation, the dog flung himself down at the bottom of his cage and refused to bite.
Two youths then threw a cord with a slip loop over the dog, as a lasso is thrown. The animal was caught and drawn to the edge of the cage. There they managed to get hold of him and to secure his jaws; and the dog, suffocating with fury, his eyes bloodshot, and his body convulsed with a violent spasm, was extended upon a table and held motionless, while Pasteur, leaning over his foaming head, at the distance of a finger's length, sucked up into a narrow tube some drops of the saliva. In the basement of the veterinary surgeon's house, witnessing this formidable tête-à-tête, I thought Pasteur grander than I had ever thought him before.