In like manner, if recent theories on the propagation of disease by germs were proved to be correct, and if the laws which govern the propagation or destruction of those germs were known, the art of the physician would be similarly raised. Upon these questions leading scientific men all over the world were devoting their energies. Research had shown that putrefaction was only another form of organized life, and Tyndall had shown that in the moving particles of fine dust discovered by a ray of light in a dark room the germs of low forms of life, which would cause putrefaction, were ever present, and ready to spring into life when a favorable "nidus" for the development of the organism was provided. Professor Lister had turned this knowledge to useful account in surgery in causing the air to be filtered by means of a carbolic spray during surgical operations, by which means germs or organisms in the air were prevented from reaching the wounds, and from developing organisms, the presence of which caused putrefaction or suppuration. This antiseptic treatment, which had arisen from the observation of germs in the air, had had a material influence on the art of surgery throughout the world. The speaker then reviewed the declarations of physiologists regarding the theories that some diseases arise from minute organisms in the blood--Pasteur holding that the disease in silkworms was from this cause; Dr. Davaine, that splenic fever in cattle arose thus; Dr. Klein alleging that pig typhoid was due to an organism; Toussaint attributing fowl cholera to a similar cause; Professor Koch attributing tubercular disease to specific germs; Dr. Vandyke Carter contending that there was a connection between the presence of bacillus spirillum and relapsing fever; and Mr. Talamon claiming to have discovered that diphtheria was due to an organism by means of which the virus could be conveyed from human beings to animals, and _vice versa_. Taking another branch of the same subject, the causes of zymotic diseases being traced to controllable sources, he said: Drs. Klebs and Crudelli allege that malarial fever arises from germs present in the soil and which float over the air of marshes; and that by treating with water the soil of a fever-haunted marsh of the Campagna the germs of this organism could be washed out; and that the water containing the organisms thus obtained, introduced into the circulation of a dog, produced ague more or less rapidly, and more or less violent, according to the numbers in which the organisms were present in the water.