PRESIDENT'S ADDRESS. Ixi. 



certainty should be arrived at before we commence the 

 violent crusades against flies which have been advocated. 

 I am not now speaking of other countries which may be less 

 fortunate. Our ignorance is well exemplified by the fact 

 that it is not yet known whether the common housefly 

 hibernates in the perfect state or not. And may I here allude 

 to the fact that the common housefly cannot bite, and that 

 it is only comparatively few flies that have a biting or rather 

 piercing apparatus, or ever use it on human beings ? But 

 an interesting association of non -biting flies with biting ones 

 has been lately noted in India. The former attend on the 

 latter and benefit by sucking up blood which the biting flies 

 have drawn from the animal after or even before the latter 

 have finished their meal. I am not aware that this has been 

 observed in England. Again, if flies were responsible to 

 any appreciable extent for the mechanical conveyance of 

 disease germs, how could cows and other animals ever be 

 free from all the available diseases, considering the swarms 

 of flies that are always on them, piercing their skin and devoting 

 special attention to any raw part. I cannot say, of course, 

 that such infection never occurs ; but it seems to me that 

 it must be most exceptional. The conveyance of germs, 

 especially those of tuberculosis in milk, seems still to be a 

 matter of some uncertainty, and as raw milk is stated to be 

 undoubtedly better for the general health and strength of 

 babies than sterilised milk it has been lately urged in 

 authoritative quarters that it should be used, the risk of 

 infection, if any, being at all events very small. The 

 sterilising doubtless kills the milk as well as the germs. In 

 the same way, in experiments on the subject of spontaneous 

 generation of life, the substances experimented with have 

 first to be sterilised to kill all germs, and if such a thing as 

 spontaneous generation does exist, of which I believe there 

 is absolutely no reliable evidence, the sterilising would 

 probably destroy any latent tendencies existing in the 

 substance dealt with, and prevent its manifestation. The 

 causes of the abundance or scarcity of any species of insect 



