STRUCTUEE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 401 
against the spread of the infection by flies, or the same would 
apply to the typhoid bacillus, whose carriage by flies is 
proven. Axenfeld mentions L. Muller and Lakah and Khouri 
as advocating the view that flies may spread the infection 
more readily. In view of the fact that, as the same author 
states, “ Koch-Weeks conjunctivitis is’ to be classed with the 
most contagious infectious disease which we know of,” it is 
important that the role of flies should be fully recognised. 
Notwithstanding the occurrence in this country of flies in less 
numbers than in such counti'ies as Egypt, it would be well to 
bear in mind the j)robable influence of flies in cases of acute 
conjunctivitis, such as those desciibed by Stephenson (1897) 
in our own country. The sole difference between the disease 
in Egypt and here is, as Dr. Bishop Harman points out to me 
in a letter, that “ the symptoms produced (in Egypt) are, from 
climate and dirtiness of the subjects, more severe, and that 
there is found a greater number of cases of gonorrhoeal 
disease than in England”; and, I would add, a far greater 
number of flies. This disease is eminently suited for dissemi- 
nation by flies, both on account of the accessibility of the 
infectious matter in the form of a purulent discharge from 
the eyes and on account of the flies’ habit of frequenting 
the eyes. 
6. Plague. 
Although fleas are considered to be the chief agents in the 
dissemination of the plague bacillus in spite of the fact that 
the proof is not absolutely convincing, it is nevertheless 
interesting, and certainly not unimportant, to refer to the 
series of experiments of Nuttall (1897) on M. domestica. 
In these experiments he conclusively proved that flies were 
able to carry the plague bacillus, and that they subsequently 
died of the disease. Flies were fed upon the crushed organs 
of animals which had died of plague. Control flies were fed 
in a similar manner on the organs of uninfected animals, and 
the control experiments were kept under the same conditions. 
