current at the wound, multiply with such prodigious rapidity that the whole system gives evidence of their existence.  Suppuration of wounds is undoubtedly due to these organisms, as is tubercular disease, whether of surgical or medical character.  Tetanus, erysipelas, and many other surgical conditions have been almost proved to be the result of infection by similar microscopic plants, which, though acting in the same way, have various forms and life histories.

A distinction must be made between the “yeast plants,” one of which produces thrush, and the “mould plants,” the existence of which, as parasites in the skin, gives rise to certain cutaneous diseases.  These two classes of germs are foreign to the present topic, which is surgery; and I shall, therefore, confine my remarks to that group of vegetable parasites to which the term bacteria has been given.  These are the micro-organisms whose actions and methods of growth particularly concern the surgeon.  The individual plants are so minute that it takes in the neighborhood of ten or fifteen hundred of them grouped together to cover a spot as large as a full stop or period used in punctuating an ordinary newspaper.  This rough estimate applies to the globular and the egg-shaped bacteria, to which is given the name “coccus” (plural, cocci).  The cane or rod shaped bacteria are rather larger plants.  Fifteen hundred of these placed end to end would reach across the head of a pin.  Because of the resemblance of these latter to a walking stick they have been termed bacillus (plural, bacilli).

The bacteria most interesting to the surgeon belong to the cocci and the bacilli.  There are other forms which bacteriologists have dubbed with similar descriptive names, but they are more interesting to the physician than to the surgeon.  Many micro-organisms, whether cocci, bacilli, or of other shapes, are harmless, hence they are called non-pathogenic, to distinguish them from the disease-producing or pathogenic germs.

As many trees have the same shape and a similar method of growing, but bear different fruits—­in the one case edible and in the other poisonous—­so, too, bacteria may look alike to the microscopist’s eye, and grow much in the same way, but one will cause no disease, while the other will produce perhaps tuberculosis of the lungs or brain.

Many scores of bacteria have been, by patient study, differentiated from their fellows and given distinctive names.  Their nomenclature corresponds in classification and arrangement with the nomenclature adopted in different departments of botany.  Thus we have the pus-causing chain coccus (streptococcus pyogenes), so-called because it is globular in shape, because it grows with the individual plants attached to each other, or arranged in a row like a chain of beads on a string, and because it produces pus.  In a similar way we have the pus-causing grape coccus of a golden color (staphylococcus pyogenes aureus).  It grows with the individual plants arranged somewhat after the manner of a bunch of grapes, and when millions of them are collected together, the mass has a golden yellow hue.  Again, we have the bacillus tuberculosis, the rod-shaped plant which is known to cause tuberculosis of the lungs, joints, brain, etc.