with the addition of salts from the earth, appearance of growth is due to the heap- 



An evolutionary query might then arise ing up of the individuals. To the naked 



as to the early conditions in the history of eye the cells are invisible, but the mass is 



organic life on the earth. It is certainly a recognized in the same way that one 



fertile field for the theorist. Accepting would know a field of wheat in the dis- 



the general rule that simplicity of struc- tance without being able to see each sep- 



ture indicates priority, what then was the arate plant. Species of bacteria are sep- 



food supply of the primordial bacterium arated by distributing a few organisms 



before the advent of higher plants to sup- throughout a fluid and then planting upon 



ply requisite organic matter? We can solid media. The individual cells then 



hardly believe that there was already in grow in place and produce colonies. 



existence sufficient ammonia-bearing These are v separate and distinct to the 



compounds of suitable quality to sustain eye and each contains bacteria, all of the 



these lowest organisms until evolutionary same kind. From colonies transplanta- 



conditions added organisms . having the tions to tube cultures are made, and the 



capacity of collecting nitrogen and car- species is propagated on different media. 



bon from purely inorganic sources. . The observations from such growths, to- 



These general facts, as we now see them, gether with the microscopical study dnd 



would apparently strengthen the thought sometimes inoculation experiments on 



that different kinds of organisms became animals are the data by which the species 



extant at the same time. is recognized. Microscopic methods, al- 



The methods used in bacteriologic though somewhat complicated have been 



study are based on a few very distinct so far developed that some species of bac- 



principles. Successful cultivation of bac- teria can be as promptly recognized un- 



teria depends upon a knowledge of sterili- der the microscope as an acquaintance 



zation, preparation of culture media and met upon the street. 



isolation of species. It is in fact minia- Bacteriology is now being studied and 



ture gardening. A rod of platinum wire investigated as a field of research in hun- 



is the trowel and this is kept clean and dreds of laboratories, and in every uni- 



free from undesirable organisms by heat- versity in Europe and America. Bacteriol- 



ing it red hot in the gas flame. With it ogy has added as much to man's wealth 



bacteria are lifted from tube or plate. The and happiness as any of the applied 



culture media required are mostly beef- sciences. All the methods of preservation 



tea and gelatine mixtures and are pre- of food depend upon bacteriological 



pared with extreme care as to their com- principles, while modern sanitary science 



position and reaction. The decomposi- is based on the recognition of the cause 



tion of the culture medium is prevented by of infectious diseases. The presence of 



keeping it in test tubes or flasks plugged specific bacteria in the secretions or 



with cotton and sterilized by boiling. By tissues of man and animals is now such a 



means of the cotton plug the air passing certainty for many diseases that the work 



in and out of the tube is filtered and the of making bacteriologic diagnoses is in 



bacteria floating in the air are caught in itself an extensive vocation. Within the 



the cotton and cannot get into the tube, next few years every city in America will 



It also prevents bacteria from the culture have a diagnosis laboratory for infectious 



getting out of the tube and spreading in- diseases. We can safely predict that the 



fectious material. Each test tube repre- trained bacteriologist will be called upon 



sents a little greenhouse, but one that is to stand between each sick person or ani- 



free from all life ; it is sterile when ready mal and the community to direct meas- 



for use. To the media or culture soils in ures that will prevent infection of others, 



the tubes the bacteria are transplanted Hygienists are learning more every day 



with the platinum rod, and active growth as to the exact way in which disease bac- 



is obtained by placing the tubes in a suit- teria pass from person to person, and the 



able temperature. Such a growth of bac- reasons for the occurrence of diseases 



teria in a test tube can contain many They have learned that the accidental and 



millions of bacteria, while the resulting unusual circumstance is least important, 



