XIII ATTENUATION OF VIRUS OF FOWL ENTERITIS 109 



only the sheath is left. (Fig. 50 shows well such 

 forms.) In old broth cultures, three and more weeks 

 old, filamentous and cylindrical bacilli are met with 

 numerously, which clearly show the granular de- 

 generation and gradual disappearance of the proto- 

 plasm, so that then only the empty sheath is left. Such 

 forms contain spherical or oval or irregular granules, 

 which still take the dye ; but the older the culture, 

 and the more numerous these forms, the less likely 

 is it found that the culture has retained vitality ; that 

 is to say, the less likely is it possible to start a new 

 living sub-culture from them. I have made a large 

 number of experiments, and have had broth cultures 

 from several weeks to several months old, in which 

 such forms (i.e. cylindrical or filamentous bacilli, con- 

 taining from place to place, in an almost empty sheath, 

 only here and there a larger or smaller stained par- 

 ticle) abounded, yet no living sub-culture could be 

 started from them. These stained particles do not 

 present any uniformity either in shape, size, or posi- 

 tion, and there would be, therefore, no justification 

 for regarding them as spores ; besides, the death of 

 old broth cultures containing those forms would clearly 

 negative their being of the nature of spores. But 

 also, by direct experiment, it is possible to show 

 that neither in the bacilli in the fowl, nor in the 

 cultures, is there anything present that is capable 



