BACTERIA. 35 



highly- refracting sphere or ovoid situated in a little col- 

 lection of granular matter. 



Spores differ from the bacteria in that their capsules 

 seem to prevent evaporation and to enable them to with- 

 stand drying and the application of a considerable amount 

 of heat. Ordinarily, bacteria are unable to resist a tem- 

 perature above 60 C. for any considerable length of 

 time, only a few resistant forms tolerating a temperature 

 of 70 C. The spores, however, are uninjured by such 

 temperatures, and can even successfully resist that of 

 boiling water (100 C.) for a short time. The extreme 

 desiccation caused by a protracted exposure to a tem- 

 perature of 150 C. will, however, destroy them. Not only 

 can the spores resist a considerable degree of heat, but 

 they are also unaffected by cold of almost any intensity. 



While the cell-wall of the bacterium is easily pene- 

 trated by solutions of the anilin dyes, it is a matter of 

 much difficulty to accomplish the staining of spores, so 

 that we see they are probably more resistant to the 

 action of chemical agents than the bacteria themselves. 



When a spore is accidentally dropped into some nu- 

 trient medium a change is shortly observed. The proto- 

 plasm, which has been clear, becomes somewhat granu- 

 lar, the capsule a little less distinct; the body increases 

 slightly in size, and in the course of time splits open to 

 allow the escape of the young organism. The direction 

 in which the escape of the young bacillus takes place is 

 of interest, as varying in the different species. The 

 Bacillus subtilis escapes from the end of the spore, where 

 a longitudinal fissure occurs; the bacillus of anthrax 

 escapes from the side, sometimes leaving the capsule of 

 the spore in the shape of two small cups. 



As soon as the young bacillus escapes it begins to in- 

 crease in size, develops around its soft protoplasm a cha- 

 racteristic capsule, and, having once established itself, 

 presently begins the propagation of its species by fission. 



In addition to the endospores, of which we have just 

 been speaking, there are arthrospores. The formation 



