of incubation is different in different animals. With regard to the human being, there are various strange and contradictory stories. Some have asserted that it has appeared on the very day on which the bite was inflicted, or within two or three days of that time. Dr. Bardsley, on the other hand, relates a case in which twelve years elapsed between the bite and the disease. If the virus may lurk so long as this in the constitution, it is a most lamentable affair. According to one account, more than thirty years intervened. The usual time extends from three weeks to six or seven months.
In the dog I have never seen a case in which plain and palpable rabies occurred in less than fourteen days after the bite. The average time I should calculate at five or six weeks. In three months I should consider the animal as tolerably safe. I am, however, relating my own experience, and have known but two instances in which the period much exceeded three months. In one of these five months elapsed, and the other did not become affected until after the expiration of the seventh month.
The quality and the quantity of the virus may have something to do with this, and so may the predisposition in the bitten animal to be affected by the poison. If it is connected with œstrum, the bitch will probably become a disgusting, as well as dangerous animal; if with parturition, there is a strange perversion of maternal affection — she is incessantly and violently licking her young, continually shifting them from place to place; and, in less than four-and-twenty hours, they will be destroyed by the reckless manner in which they are treated. In both cases the development of the disease seems to wait on the completion of her time of pregnancy. It appears in the space of two months after the bite, if her parturition is near at hand, or it is delayed for double that time, if the period of labour is so far distant.
The duration of the disease is different in different animals. In man it has run its course in twenty-four hours, and rarely exceeds seventy-two. In the horse from three to four days; in the sheep and ox from five to seven; and in the dog from four to six.
Of
real nature of the rabid virus, we know but little. It has never been analysed, and it would be a difficult process to analyse it. It is not diffused by the air, nor communicated by the breath, nor even by actual contact, if the skin is sound. It must be received into a wound. It must come in contact with some tissue or nervous fibre, and lie dormant there for a considerable, but uncertain period. The absorbents remove everything around; whatever else is useless, or would he injurious, is taken away, but this strange substance is unchanged. It does not enter into the circulation, for there it would undergo some modification and change, or would be rejected. It lies for a time absolutely dormant, and far longer than any other known poison; but, at length, the tissue on which it has lain begins to render it somewhat sensible, and assimilates to itself certain elements. The cicatrix begins to be painful, and inflammation spreads around. The absorbents are called into more powerful action; they begin to attack the virus itself, and a portion of it is taken up, and carried into the circulation, and acquires the property of assimilating other secretions to its own nature, or it is determined to one of the secretions only; it alters the character of that secretion, envenoms it, and gives it the power of propagating the disease.
Something like this is the history of many animal poisons. In variola and the vaccine disease the poison is determined to the skin, in glanders to the Schneiderian membrane, and in farcy to the superficial absorbents. Each in its turn becomes the depôt of the poison. So it is with the salivary glands of the rabid animal; in them it is formed, or to them it is determined, and from them, and them alone, it is communicated to other animals.
Dick, in his valuable