14 



primary IdiiIjo and from the pneumonic foci their number is legion. 

 In smears from the spleen thev are fairly abundant, while in 

 preparations from the other organs, according to our own experi- 

 ence, they are generally present only to a moderate extent, unless 

 septico-pyemic metastatic foci should have been established, when 

 they may be quite numerous. In smears prepared from the heart's 

 blood we have always found very few bacilli, even in pneumonic and 

 septico-p3'emic cases. 



As a routine method for the examination of smears we have 

 adopted the following procedure: The preparations were made 

 during the post-mortem examinations on slides, and these, as soon 

 as air-dr}^, were placed in a wide-mouthed bottle containing absolute 

 alcohol. Here they remained until after the termination of the 

 autopsy, when they were stained with dilute carbol-fuchsin (1 part 

 of the original stain to 5 to 10 aqua destillata) for twenty to forty 

 seconds, and then freely washed with water. They were next 

 immediately examined with oil-immersion magnification. If it 

 was found that the stain was not satisfactory, being either too light 

 or too heavy, the immersion oil was washed off in xylol and the 

 shortcomings corrected either by a second prolonged dyeing or by 

 rapid immersion in alcohol, followed by washing in water. How- 

 ever, after a little practice it is soon possible correctly to estimate 

 the time necessary to bring about that particular stain which will 

 best show the characteristic morphologic features of the bacillus, 

 and a second attempt is rarely necessary. If after the first 

 examination of the slides it is desirable to preserve them for future 

 reference, the immersion oil is washed off in xylol and the speci- 

 mens may now be mounted permanently in Canada balsam, being 

 protected by a cover slip. 



In smears made from the organs the j)lague organism appears 

 as a rather short, plumjj bacillus, being 1.5 to 1.15 fx, long and 

 0.5 to 0.75 /A thick; generally the proijortion of width to length is 

 as one to two. Individuals considerably longer than 1.75 ju, are 

 occasionally seen. The bacilli are generally single, occasionally 

 diplobacilli are encountered, and very rarely short chains. In 

 smears which have been fixed in absolute alcohol and which have 

 been jDroperly dyed the bacilli are not uniformly colored, but they 

 show a distinct polar staining. Frequently the whole periphery of 

 the bacillus is stained and only the center has remained uncolored. 

 Other forms of the organism, while differing in certain respects 



