PLATE XIX. 



BACILLUS OF DIPHTHERIA. 



FIG. i. THE "TYPICAL, 1 " KLEBS-LoFFLER," OR "LONG" DIPHTHERIA 



BACILLUS. 



Fro n a culture on Loffler's blood-serum ot twenty-two hours' age, incubated at 37 C. The 

 growth was the third sub-culture of the original from the throat. Stained with Lijffler's 

 methylene blue, washed in tap water. The case from which the culture was raised concerned 

 a boy (P. R.J, admitted to St. Thomas's Hospital, October iSih, 1897, with inflamed throat ; 

 there was much membrane on the tonsils, and in the larynx as evidenced by the stridor and 

 retraction of the chest. Tracheotomy was performed, the tube being removed on the founh 

 day. Four thousand units of diphtheria antitoxin were administered by subcutaneous 

 injection. Until the early part of November progress had been favourable ; on November 24 th 

 palatal paralysis was noted, the voice acquiring a nasal twang; this slowly improved. The 

 knee-jerks were absent on November agth, and still absent on December 24th, but the patient 

 could at that date swallow without regurgitation. 



The Bacilli are straight or slightly curved rods of varying length and thickness, often set in 

 parallel groups of two or more. The designation of "long" implies that many, not all, are of 

 conspicuous length. One end (or both) may be enlarged or bulbous ; in the absence of this, 

 the ends are abruptly rounded without tapering. The bacilli present a notable segmentation 

 of protoplasm, which is divided into deeply stained parts ; these, which may be far from 

 equidistant, are in some instances flattened across the long axis of the rod, in others, spherical. 

 The extremities of the bacillus correspond with terminal segments. In -some of the shorter 

 rods only terminal parts are dyed end or polar staining. 



The primary forms appear as short uniformly stained bacilli, with ends slightly smaller than 

 the rest of the rod ; these undergo transverse division, before the completion of which they 

 appear as diplo-bacilli with the opposed ends flattened. Segmentation rapidly takes place, 

 the shortest forms exhibiting onh end-staining ; the hitter are distinguishable from true 

 diplo-bacilli by the absence of tapering free ends and the length of unstained centre. These 

 forms of the diphtheria bacillus are classed as " typical," since they are commonly associated 

 with the typical, more virulent examples of diphtheria; yet not invariably so, for not only 

 may ''atypical" forms be highly virulent, but similar "typical" or "long" forms may possess 

 little palhogenicity (as tested upon the guinea-pig), and occur in cases which clinically present 

 no other features than those of sore throat, unaccompanied even with any marked malaise. 



Fu;. 2. "ATYPICAL" OR "SHORT" DIPHTHERIA BACILLI. 

 A culture of thirteen hours' growth on Loffler's blood serum, carried on !rom one (Viennese) 

 of the virulent strains in use at the Conjoint Laboratories of the Royal College of Physicians 

 and Surgeons, London, for the preparation of toxin employed in the production of diphtheria 

 antitoxin from the horse. Besides a few segmented forms are others of an "atypical " kind, 

 commonly ranged in parallel collections of two or more ; these mostly taper off at the 

 extremities, presenting a deeply stained centre, which is usually divided by an uncoloured 

 narrow line indicative of an incompleted transverse fission, the elements being double, or 

 diplo-bacilli. Beyond the deeply stained centre the bacillus is of a lighter blue. Here and 

 there a pyrifonn element occurs, more deeply stained towards the larger end ; or short deep'y 

 stained spindles. 



FIG. S.-A SECOND EXAMPLE OF THE "ATYPICAL" OR "SHORT" 

 DIPHTHERIA BACILLUS. 



From a virulent case of the disease. Diplo-bacilli in parallel groups ; beyond their opposed 

 deeply stained central ends the component elements taper off and are but lightly coloured. 

 Pear-shaped forms are present, and a few which exhibit polar and segmented staining. From 

 its staining reaction the form has been named the "sheath" variety by Dr. J. Eyre, to whom 

 the author is indebted for the preparation from which the figure has been drawn. The " sheath/' 

 variety occurs, as a rule, in the milder types of diphtheria. It is but rarely met with, and is 

 not strictly stable ; if grown for some days upon alkaline potato and again sown on blood- 

 scrum, it acquires the segmented characters of the "typical" form. 



Another atypical pathogenic variant has been described of the same form as the above, but 

 staining uniformly and deeply throughout. 



FIG. 4 . HOFMANN'S BACILLUS. 



Culture of twenty-four hours' on agar, incubated at 37 C. Stained with Loffler's blue, 

 washed in tap water. The culture was carried on from one isolated by Dr. E. A. Peters, 

 to whom the author is indebted for a sample of the strain. Diplo-bacilli, occurring in 

 parallel groups of two or more. The elements composing a single diplo-bacillus are short, 

 squat, wedge-shaped, with opposed bases, and stain uniformly throughout. They are 

 markedly shorter than the atypical or short varieties of the diphtheria bacillus, and relatively 

 broader at their bases. In older cultures segmented and irregular involution forms may be 

 encountered. Hofmann's bacillus (sometimes named a pseudo-diphtheria bacillus) is not 

 found as a cause of true diphtheria in the human subject. Hence, though isolated in many 

 forms of sore throat, such lesions are not to be regarded as diphtheritic. The bacillus, may, 

 however, be associated with the " typical," " Klebs-Loffler," or " long" diphtheria bacilli in 

 diphtheritic affections, but under such circumstances its presence may be regarded as of 

 secondary significance. 



