20 INSECTS AFFECTING DOMESTIC ANIMALS. 
infecting in this way of a sore on a healthy person. There is no 
doubt that ophthalmia is so spread, and an instance is given of com- 
plete destruction of an eye from diphtherial inflammation following the 
sting (bite) in the eye by a fly which had apparently risen from a 
dunghill. (Entomological News, Vol. V, p. 18.) 
The late Dr. John A. Ryder presented the following very decided 
opinion: 
Cholera and flies.—It may not be amiss to call the attention of the public to the 
great danger from house flies as agents in spreading the contagion in case there be 
an epidemic of cholera. I have repeatedly observed that these insects will ride for 
a number of miles on street cars and doubtless also upon other vehicles of transit, 
such as railway coaches, etc., though I have never made observations upon any con- 
veyance but the ordinary tram or horse car. Suppose a case: Imagine a cholera 
victim upon the street or anywhere else vomiting. The flies present are attracted 
and drink until sated, and have their feet and mouth parts wetted with the vomit 
containing the germs. They then perhaps fly out into the street, take a place on a 
horse car, ride several miles, dismount, fly into another house, where the family 
are at dinner, and contaminate the food set before them with the germs of the 
cholera carried on the mouth parts and feet of the insects. Some of the family 
sicken and die, yet no one of them will ever perhaps suspect that the flies may have 
carried the germs, as supposed above, for miles from some other case. The safe- 
guards are to at once clear away, disinfect with corrosive sublimate solution, and 
seald the spots where the vomit has been thrown, and to be vigilant in the use of 
fly-screens, fly-traps, ete. During the late war the late Professor Leidy pointed 
out, with beneficial results, that the common house fly was instrumental in spread- 
ing the contagion of hospital gangrene. Why not beware of this imprudent and 
ubiquitous little dipter in carrying and spreading the contagion of the dreaded 
Asiatic plague now menacing us?—(See Entomological News, Vol. III, p. 210.) 
The determination in recent years of the connection existing between 
the cattle tick of the Southern States and the formidable- disease 
known as Texas fever is a striking example of the importance of this 
question. This particular case is treated more fully in connection 
with the discussion of the cattle tick. | 
If we consider all contagious diseases as due to specific organisms, 
we may relegate them all to the rank of parasitic diseases, but leaving 
out all due to so-called microbes or micro-organisms as producers of 
specific diseases, we have instances where one parasite serves as the 
carrier of other and more injurious forms. For example, the louse and 
the flea of the dog have been found to serve as the intermediate hosts 
for a tape-worm (Dipylidium caninum L.) which also infests the dog, 
the tape-worm, when mature, extruding eggs which gain entrance to the 
external parasite. The dog, in licking or biting himself to destroy 
the parasites or relieve the irritation, swallows some of his tormentors, 
the young tape-worms are set free in the stomach, and there develop to 
maturity. 
LOSSES DUE TO PARASITES. 
It is practically impossible to make any accurate estimates of the 
losses resulting in a great many of the forms of insect attack upon 
domestic animals. Naturally, no notice is taken of their presence or 
