STUDIES ON SIMPLE AND DIFFERENTIAL METHODS 



OF STAINING ENCAPSULATED PNEUMOCOCCI 



IN SMEAR AND SECTION * 



Augustus Wadsworth, 



Alonzo Clark Scholar in Pathology; Instructor in Bacteriology and Hygiene, College of Physicians and 

 Surgeons, Columbia University, Assistant Physician to the Roosevelt Hospital Outpatient 



Department. 



{From the Department of Pathology, College of Physicians and Surgeons, Columbia University.) 



In the course of some experimental studies on pneumococcus 

 infection, the technic of previous observers recommended for the 

 staining of the encapsulated organisms was tested, and various 

 new methods were devised in the hope of securing rehable proced- 

 ures by which pneumococci may be dififerentially stained in cover-glass 

 preparations and in sections of tissue. 



My experience with these methods, old and new, it is the purpose 

 of this paper to record. 



PREVIOUS METHODS. 



Simple staining. — In the simplef routine staining with aqueous- 

 gentian-violet or carbol fuchsin, smears of pneumococcus exudates 

 may show the organisms encapsulated; but this is extremely uncer- 

 tain. Similarly, under favorable conditions many of the older 

 special methods;|: devised for capsule staining often give excellent 

 preparations, but the results vary, and are therefore unreliable 

 when compared with those obtained with the simple, perfected 

 technic used by recent observers. The most reliable and practical 

 of all these methods in my experience are based wholly or in part 

 on principles first adopted by Guarnieri. 



In 1888 Guarnieri 5 made determinations of the solubility of 

 the pneumococcus capsule in acid, alkaline, and neutral salt solu- 

 tions; and finally he obtained the proteid reaction with Millon's 

 reagent, thus indicating an albuminous composition. On these 

 determinations Guarnieri devised a new method of staining the 

 encapsulated organisms in exudates: smears fixed in the flame 



♦Received for publication February 19, 1906. 



tPane." 



iFriedlander,^ Ribbert.'J Roux,'* Muir," MacConkey,' Gordon,* Kolle and Wasserman.' 



304 



