262 THE INFECTIOUS DISEASES. 



marked irregularities in its form (Fig. 134). While tbe typical form is that of a 

 round-ended, straight, or slightly curved bacillus, it is very apt perhaps as a re- 

 sult of degeneration to appear club-shaped or pointed at the ends, irregularly seg- 

 mented, and to develop at the ends or elsewhere a strongly refractile material which 

 stains more deeply than the rest of the protoplasm. 



The diphtheria bacillus is immobile, asporogenous, grows best at blood heat, and 

 thrives on most of the artificial culture media. In fluids it may be killed by an expos- 

 ure of ten minutes to a temperature of 58 C. ; but it may remain alive for weeks, or 

 even months, in fragments of dried membrane. It may be stained with Loffler's alka- 

 line methylene-blue solution or by Gram's method. 



It is subject to extreme variations in virulence, forms occurring which with all the 

 usual cultural characteristics are not at all virulent.' 



Action of the Bacillus in Animals. 



inoculations of virulent cultures subcutaneously in guinea-pigs are followed by a 

 localized hemorrhagic osdema with a variable amount of whitish exudate. Death usu- 

 ally occurs in from two to five days. In addition to the local lesions there may be but 

 this is not constant swelling of the adjacent and of the abdominal lymph-nodes, serous 

 effusions into the pericardial, pleural, and peritoneal sacs; swollen spleen, albuminous 

 and fatty degeneration in the liver, kidney, and heart muscles; congestion and some- 

 times hemorrhage of the suprarenals. Microscopical examination shows, in a consider- 

 able proportion of cases, fragmentation of nuclei and other evidences of cell death at the 

 seat of inoculation and in the viscera, as well as chromatolysis of ganglion cells in the 

 anterior horn. Animals which survive the inoculations may later develop paralysis, 

 and a similar result may follow the injection into rabbits of culture fluids. The bacilli 

 do not usually gain access to the body at large, but may be found at the seat of inocula- 

 tions. Inoculation into the mucous membranes of rabbits, pigeons, and certain other 

 animals may result in the development of a pseudo-membrane somewhat resembling 

 that of the disease in man. 



Diphtheria Toxin and Antitoxin and Diagnosis. 



We have already considered the action of antitoxin on page 175 and need not dwell 

 upon it here. POT methods of the manufacture and tests of antitoxin, consult Park, 

 "Bacteriology in Medicine and Surgery." 



For details of bacterial diagnosis consult works on bacteriology or clinical path- 

 ology. 



The agglutinative reaction of the diphtheria bacillus is not sufficiently definite to 

 permit of its use in diagnosis. 



It is important from the prophylactic standpoint to remember that the Bacillus 

 diphtheria? may remain alive in the mouth of the human subject for many weeks after 

 recovery from the local lesions of the disease, and also that healthy persons when the 

 disease is prevalent may harbor the virulent bacilli in their mouths. 2 



1 For a study of varieties of the B. diphtheria?, see Williams, Jour. Med. Research, 

 vol. viii., 1902, p. 83; see also for full summary of studies on the diphtheria bacillus 

 and its toxins, Beck, Kolle and Wassermann's "Handbuch der Mikroorganismen," Bd. 

 ii., p. 754. 



* See for a study of the diphtheria bacillus in the mouths of health}' persons and 

 those exposed to the disease Graham-Smith, Jour, of Hygiene, vol. iii., p.' 216, bibl. 



