TYPHOID BACILLI IN TISSUES. 227 



instances led to the belief that the pale, unstained portions 

 of the bacilli indicate the presence of spores. More 

 exact tests, however, have demonstrated the error of this 

 opinion. 



It grows at any temperature between 20 C. and 

 38 C., though more favorably at the latter point. 



It is very sensitive to high temperatures, being killed 

 by an exposure of ten minutes to 60 C., and in a much 

 shorter time to slightly higher temperatures. 



Owing to a tendency toward retraction of its proto- 

 plasm from the cell envelope and the consequent pro- 

 duction of vacuoles in the bacilli, the staining of this 

 organism is usually more or less irregular. At some 

 points in a single cell marked differences in the intensity 

 of the staining will be seen, and here and there areas 

 quite free from color can commonly be detected. 



PRESENCE IN TISSUES. It is not easy to demonstrate 

 this organism in tissues unless it is present in large num- 

 bers. The manipulations to which the sections are sub- 

 jected in being mounted rob the bacilli of their staining, 

 and render them invisible, or nearly so. If, however, 

 sections be stained in the carbolic- fuch sin solution, either 

 at the ordinary temparature of the room for from eigh- 

 teen to twenty hours, or at a higher temperature 

 (40 to 45 C.) for a shorter time, then washed out in 

 absolute alcohol, and cleared up in xylol and mounted 

 in balsam, as a rule, the bacilli (particularly if the tissue 

 is the liver or spleen) can readily be detected massed 

 together in their characteristic clumps. If used in the 

 same way, the methylene-blue solution gives also very 

 satisfactory results. 



In searching for the typhoid bacilli in tissues, their 



