3IO Augustus Wadsworth 



strate capsules on such cells, albumin* in the form of blood serum 

 (Hiss) or egg albumin (Boni) must be added, and thoroughly mixed 

 with the sputum before the smears are made. The mucus in which 

 many of the organisms are imbedded protects them from the albu- 

 min, and they fail to show capsules. Often it is only the isolated 

 or exposed cells which show capsules. In the fixation by formalin 

 the mucus also protects the cells from the action of this reagent; 

 longer exposure is therefore required, and after this the preparation 

 should be thoroughly washed in water, or some of the formalin 

 will be retained and precipitate the anilin stain when this is used. 



The demonstration of capsules on the pneumococci in sputum 

 thus depends primarily upon bringing the bacterial cells into an 

 albuminous environment favorable to the preservation or develop- 

 ment of capsules. t This accomplished, the staining procedure is 

 purely a matter of choice. With the formalin preparations the 

 Gram stain may be used and a differentiation for practical purposes 

 at once secured, as on further study in culture, Gram-positive, 

 encapsulated organisms of pneumococcus morphology practically 

 always give the biological characters of the pneumococcus. Occa- 

 sionally encapsulated forms of the Micrococcus tetragenus resemble 

 atypical pneumococci, but usually there is little difficulty in differ- 

 entiating these forms. The Streptococcus mucosus, in my experi- 

 ence, cannot be differentiated morphologically from the pneumo- 

 coccus. Streptococci, in my experience, have rarely given definite 

 capsules;}; with these formalin methods. 



THE TECHNIC FOR SECTIONS OF TISSUES. 



Although the fixation of the pneumococcus capsule in smears 

 is simple, in tissues hardened for celloidin sections it is difficult 

 and less certain. The chief difficulty lies in securing sufficient 

 penetration. In the body fluids the formaHn is diluted, and it 

 combines with the albuminous material which is coagulated. This 



*Blood serum seems to mix with sputum better than egg albumin, but as suggested by Professor 

 F. C. Wood, egg albumin, if it is diluted and made isotonic with NaCl solution, will give practically as 

 good results. 



tVVith some pneumococci capsules are obtained with great difficulty. For complete discussion of 

 the dififerentiation of the pneumococci the reader is referred to the work of Hiss, Borden, and Knapps. 



^Occasionally a faint, hazy periphery, suggesting a shrunken or degenerated, partially dissolved 

 capsule, was noted. 



