Mention has already- been made of ba cilli found in cultures resembling the diphtheria bacillus and yet not possess ing the specific pathogenic properties of that bacillus, and therefore termed pseu dodiphtheria bacilli. This term is most unfortunate, since these bacilli bear no ' relation to the throat inflammation termed pseudodiphtheria. As seen in cover-glass preparations, these bacilli are shorter, plumper, and more uniform in size and staining. They are most often met with in cultures from the nose. When obtained in pure cultures, these bacilli have been shown to be devoid of virulence.
As seen under the microscope, the uni formity in size, shape, and staining is sufficiently marked from the variations in these points noted with reference to the diphtheria bacillus to enable ticed observers to recognize them readily.
In the diagnosis of diphtheria the sim ple microscopical method of examining the exudate is a great deal better than any clinical method. All that is needed is a good microscope, with an Abbe con denser and oil-immersion lens. Also a few slides are required, and some Loftier alkaline blue. If one meets with a sus picious case, all that is necessary is to ask for a whalebone or stout stick and wrap a bit of absorbent cotton on the eml. This swab should be rubbed on the exudate very firmly; then it can be put in an envelope or otber simple container and examined in the office. To do this. one should moisten a clean glass slide with a drop of water and rub the swab around in it for a minute. Then the swab Should be burned and the prepara tion dried. When it is thoroughly dry. it is passed through a flame three times at such a rate that the exudate is baked and will not wash off. On the other hand, it should not be heated so that the preparation is distorted and scorched. After heating, one should run on the slide a. drop or two of Daces blue, sufficient to cover the dried exudate, then wash off the stain. dry thoroughly with blotting-paper, and drop on a little cedar-oil and examine. The whole process takes about a minute or two.
lf the ease is diphtheria, the first thing that will attract the eye are masses of fibrin stained deeply blue. These masses are stringy in texture. In these masses of fibrin and outside pecul iar bacilli may be seen. They are al ways more or less curved. They are never of perfectly even width. They are
often clubbed at one or both ends, or they may taper at one or both ends. These organisms never take the stain evenly; the substance of the bacilli appears much denser in places, so that the organism appears to have bands or stripes. Bacilli often appear broken in the middle. or there seems to be an achromatic juncture.
But what is far more characteristic is the presence of little black or bluish black points very often situated at one or both poles of the bacilltis, with occa sionally ft little point in the middle. If these point-bearing bacilli are folind in the fibrin, one can be very certain that the case is diphtheria. There are many other organisms found in diphtheritic membrane by this method, but if they contain chromatin granules and are curved and irregular in outline, they are diphtheria bacilli. If the case is ton sillitis, by the same method single round cocci or streptococci or diplococei are to be found, but no chromatin point-bear ing little rods will be seen.
A diagnosis of diphtheria should not be made unless these chromatin points are found. The preparation should be properly heated, and it is most impor tant that the stain be good. A poor stain will not differentiate the chroma tin points. Chromatin points appear in other organisms, as has been seen in long bacilli grown on potato and found in water, but the organisms were three or four times longer than the diph theria bacillus; they WCI'C straight and of eyen width, except where the chro matin points bulged through the con tinuity, so that the organism resem bled a jointed bamboo cane. It is said that a bacillus wide]] is pathogenic for mice also exhibits ehromatin spots. But it is rare to find such organisms in the throat, and mitch rarer to find them in psendornembrane. 11. Pitfield (Univ. of Penna. Med. Bull., Sept., 100]).
Whenever we find the characteristic bacilli above described present in the cover-glass preparations, we can safely set the case down as one of true diph theria, however few the bacilli may be in number in the smear, or with what ever other bacteria combined. If the diphtheria bacilli are found at all, a second culture usually shows them greatly exceeding in numbers any other form of bacteria present, and the cases will be found to present the clinical symptoms of diphtheria.