Specificity 469 



from the sick-room to the outer world. Still more extra- 

 ordinary are the observations of Hewlett and Nolen,* that 

 the bacilli remained in the throats of patients seven, 

 nine, and in one case twenty-three weeks after convalescence. 

 The hygienic importance of this observation must be ap- 

 parent to all readers, and serves as further evidence why 

 thorough isolation should be practised in connection with the 

 disease. 



Neumann f found that virulent diphtheria bacilli may 

 occur in the nose with the production of what seems to be 

 a simple rhinitis as well as a pseudo-membranous rhinitis. 



Fig. 152. Wesbrook's types of Bacillus diphtheriae: a, c, d, Granular 

 types; a 1 , c 1 , d 1 , barred types; a 2 , c 2 , d 2 , solid types. X 1500. 



Such cases, not being segregated, may easily serve to spread 

 the contagion of the disease. 



Wesbrook, and Wilson and McDaniel J have found it con- 

 venient to describe three chief types of the diphtheria 

 bacillus as it occurs in twenty-four-hour-old cultures on 

 Loffler's blood-serum, sent to the laboratory for diagnosis. 

 The classification places all types in three general groups: 

 (a) granular, (6) barred, and (c) solid or evenly staining 

 forms. Each group is subdivided into types based on the 



*"Brit. Med. Jour.," Feb. i, 1896. 



t "Centralbl. f. Bakt. u. Parasitenk.," Jan. 24, 1902, Bd. xxxi, 

 No. 2, p. 41. 



J "Trans. Assoc. Amer. Phys.," 1900. 



