The bacteriological condition of the wound is expressed by a fraction in which the numerator gives the number of microbes observed, while the denominator shows the number of fields examined.

Graphically, the bacteriological state may be represented on a chart, where time is shown in the abscissae, and the number of microbes contained in a microscope field in ordinates (Fig. 68). As it frequently happens that only a single microbe is seen for two, five, or ten fields, this is expressed by 1/2, 1/5, or 1/10 microbe per field.

Each patient has a chart which informs the surgeon concerning the condition of the wound day by day.

4th. Causes of Error. - Certain mistakes should be avoided when taking specimens. In the first place, haemostasis must be absolute at the moment of taking the specimen. When the secretions are diluted by blood, microbes can no longer be discerned. It is for this reason that the "smear" method gives no indication in the great number of cases as to the state of infection of fresh wounds.1

So long as haemorrhage persists, it is useless to make smears. Again, in examining wounds of longer standing, it is necessary to take the specimens at a time when the secretions are not diluted by hypochlorite, and from regions where infection still persists. The smooth surface of muscles is rapidly sterilised, so that specimens taken in those regions do not give a true idea of the real state of the wound. Many specimens from different regions of the same wound must be taken, to avoid error.

Fig. 68.   Microbial Chart. In the upright columns are noted the number of microbes found per microscope field, varying from infinity to 1 and from 1 to 1/20. A twentieth implies one microbe per twenty fields of the microscope. The upper horizontal column marks the date.

Fig. 68. - Microbial Chart. In the upright columns are noted the number of microbes found per microscope field, varying from infinity to 1 and from 1 to 1/20. A twentieth implies one microbe per twenty fields of the microscope. The upper horizontal column marks the date.

1 Ignorance of this detail has caused certain surgeons to believe that fresh wounds are not infected.

PLATE I.

Fracture of the femur in its middle portion by a ball (Case 522). Fig. 69.   May 28. Rod like bodies in immense numbers. Fig. 70.   May 31. The rods have almost disappeared, and have been replaced by an immense number of cocci. Fig. 71.   June 3. About 30 cocci per microscope field. They are usually in clusters. Fig. 72.   June 7. 10 to 15 cocci per microscope field. Fig. 73.   June 13. About 2 microbes per field. Fig. 74.   One coccus to 10 or 20 fields of the microscope. The wound is aseptic. (The illustrations represent only the central portion of the field of the microscope.) ' To face page 186.

Fracture of the femur in its middle portion by a ball (Case 522). Fig. 69. - May 28. Rod-like bodies in immense numbers. Fig. 70. - May 31. The rods have almost disappeared, and have been replaced by an immense number of cocci. Fig. 71. - June 3. About 30 cocci per microscope field. They are usually in clusters. Fig. 72. - June 7. 10 to 15 cocci per microscope field. Fig. 73. - June 13. About 2 microbes per field. Fig. 74. - One coccus to 10 or 20 fields of the microscope. The wound is aseptic. (The illustrations represent only the central portion of the field of the microscope.) ' To face page 186.

B. Results Of The Examination

The examination of the wound allows us to estimate, according to the bacteriological condition and the anatomical elements present in the secretions, the degree of sterilisation of the wound. By counting every two or three days the microbes contained in secretions taken from different parts of the wound, and by studying the evolution of the leucocytes, the progress of sterilisation can be followed.

1st. Modifications of the Bacteriological Condition of the Wound, {a) Fresh Wounds. - Smears from wounds less than twelve hours old rarely show microbes. They are only found in the immediate neighbourhood of shreds of clothing on the surface of crushed muscle, and are usually rod-like bodies. They are very few in number, and the microscope field has to be moved several times to discover one. Occasionally when the wounds are six or eight hours old, the smears yield microbes plentifully. If no microbes are seen in the secretions of a fresh wound, it will not do to conclude that the wound is sterile, but simply that the microbes are still few in number and so diluted by blood that they cannot be seen. Experiment has demonstrated that, in cases where the smears are negative, cultures made from fragments of shell or clothing, debris of muscle or connective tissue taken from the immediate vicinity of foreign bodies, give positive results. Almost always, anaerobic cultures made under these conditions produce gas. It might be said that every shred of cloth can determine a gas infection.

At the end of twenty-four or thirty-six hours, the secretions of the wound often yield microbes (Figs. 69 and 75). The topographical variations of infection are less marked, and these differences diminish as the secretions become more abundant. Twenty-four or forty-eight hours after the commencement of instillation of hypochlorite, the topography of infection and its volume are modified. The surface of normal muscle only shows half a score microbes per field, whilst they are beyond counting on the surface of fractured bone and especially in the debris of necrosed muscular or cellular tissue. After two, four, or six days, the greater part of the surface of the wound is sterile, but microbes remain on irregular bony surfaces, and in deep culs-de-sac which have not been reached by the liquid (Figs. 71 and 72). Fragments of necrosed tissue still contain the same quantity of microbes. The moment the solution of these tissues by the hypochlorite is achieved, there is an abrupt drop in the bacteriological curve, and sterilisation will then be complete in one or two days.