3O0 Augustus Wadsworth 



The methods of Guarnieri, of Welch, and of Buerger, rehable, though 

 in one way or another compHcated, all give temporary mounts, 

 and are thus unsatisfactory; particularly when similar or better 

 results may be secured by simpler procedures giving permanent 

 preparations in balsam, which may be kept for future reference, as 

 vdth the copper sulphate method of Hiss.^ 



Dijjerential staining. — These simple methods of staining encap- 

 sulated pneumococci, however, do not always suffice to differentiate 

 the pneumococcus from other capsule-forming bacteria.* To com- 

 plete this differentiation further steps are necessary. In pneumonic 

 exudates, pneumococci, streptococci, and pneumobaciUi (Fried- 

 lander) are frequently associated together. The streptococci, 

 except possibly under especially favorable conditions, rarely show 

 capsules. The pneumobaciUi not only are encapsulated, but the 

 short and degenerating forms are practically indistinguishable 

 from the pneumococci. The pneumobacillus, however, decolorizes 

 by the Gram stain ; but this does not show capsules, and when these 

 contaminated exudates are examined for the morphological deter- 

 mination of the presence of these species, both the capsule and the 

 Gram stains are required, and even then the observations may not 

 be accurately correlated. Cultural characters are more precise and 

 final, but require time; and, furthermore, the streptococci and 

 pneumobaciUi, when present, usually predominate; they also grow 

 so rapidly, and the pneumococci are frequently in such small numbers, 

 that, unless exceptional precautions are taken, the pneumococci may 

 not be found. 



For these reasons efforts have been made to obtain a rehable 

 method which would demonstrate the capsules and the Gram differ- 

 ential in the same preparation. This result has been noted in speci- 

 mens overexposed, or exposed with heat to the anihn stain and the 

 iodine solutions; but this is so exceptional that special methods 

 have been devised. 



For this purpose Smith's fixes the smears of fresh sputum from 

 pneumonia patients in the usual way by heat. The films are then 



♦The morphological differences in the capsules of the pneumococci, as compared with other encap- 

 sulated organisms resembling the pneumococcus, which Buerger obtained with his simple stain, and upon 

 which he lays so much stress, depend chiefly upon the varying stages of development or degeneration and 

 solution of the capsule, and upon the degree of decolorization. They are in no sense differential. 



