264 MICRO-ORGANISMS AND DISEASE [chap. 



Microscopic Examination of the Cultures. 



With the cultures above described cover-glass specimens 

 may be made in the usual way, i.e. a thin film of the fluffy 

 or floccular precipitate from the broth cultures, or of the 

 precipitate from the Agar condensation fluid, is prepared by 

 drying and staining ; and this is found to exhibit the bacilli 

 in long twisted chains and threads, aggregated so as to 

 form dense networks and convolutions or frequently forming 

 bundles (Fig. loo). Many of the threads are found to 

 measure several millimetres in length, while some are 

 broken up into shorter bits. The threads are formed by 

 the individual bacilli placed end to end, the sheaths of the 

 bacilli forming a continuous sheath for the thread ; in the 

 stained specimens each element is marked either as a 

 minute rod or more commonly as a dumb-bell of granules, 

 this appearance being due to the polar granules of the 

 individual bacilli being very strongly marked : or, by stain- 

 ing this dried film in carbolmethyl-blue for about half to one 

 hour, and then washing in water, drying, and mounting in 

 balsam, the character of the bacilli in the threads may be 

 very well seen. 



In recent cultures the threads are either wholly or 

 partially made up of bacilli which stain at the two 

 poles ; such elements as do not show this character ap- 

 pearing as uniform rods about 0*4 /a in thickness, o'8 to 

 V2 ftu'm. length. Cultures several days old show many of 

 the threads already degenerating ; that is to say, shorter or 

 longer portions being empty of protoplasm showing only the 

 faintly stained sheath with here and there indistinct granules 

 in it. But in all specimens made of however recent a 

 culture there are threads, in which. here and there a bacillus 



