Communication of glanders from one horse to another with which it may be in contact is a fact which is hardly questioned in the present day, but it is also true that in many cases a glandered horse has been kept in a stable with a number of others without any extension of the disease so far as an ordinary clinical examination would enable an observer to determine. This circumstance has been noted by some of the older writers. On the other hand, recent investigations prove that the period of incubation, by which term is meant the period which elapses between the introduction of the virus and the declaration of the disease, is exceedingly variable, although it has been stated by different writers that it may extend from a few days to a year.