FIG. 20. Bacillus subtilis. 



Cover - yhisn preparation 

 from an Hyht-days old 

 L; hit in culture ^rown 

 at room temperature. 

 Stained with Vesiivine. 

 The spores, not having 

 absorbed the dye, show- 

 up as white specks 

 against the (dark, 

 stained) vegetative cells. 

 (After 

 Magn. 950. 



ARTHROSPORES 



cell, that behaves similarly towards dyes is to be considered as an 

 whereas it is not yet proved that spores alone 

 exhibit this power. A general report concerning the 

 spore formation in any bacillus must therefore be received 

 with due reserve when it rests merely on the result of 

 staining experiments. The sole decisive proof of the 

 sporous nature of such bodies is afforded by their ger- 

 minating power alone, a subject discussed in the n< tt 

 chapter. When this property has been observed, the 

 staining flask is no longer needed, its use in such case 

 being confined to the preparation of a coloured slide, 

 which, in itself, is now valueless as a criterion. 



The property of offering considerable resistance to 

 decolorising agents, possessed by the endospores, is also 

 shared by the vegetative forms of a few species of bac- 

 teria, among which are the tubercle bacilli and the leprosy 

 bacilli. This unusual behaviour greatly facilitates their 

 detection by microscopical examination alone, and is of 

 particular utility in this respect in the examination of 

 milk and of the sputa of consumptive patients. 



The differential staining of tubercle bacilli, also ex- 

 perimentally applied to non-pathogenic bacteria by many bacteriologists, will be 

 found dealt with in each of the above-named books. 



55. Arthrospores. 



As already remarked, the capacity for forming endogenous spores is not 

 universal among the fission fungi. The question then arises as to the means 

 whereby those species not endowed with this faculty protect themselves agaiiibt 

 adverse external influences. 



In many cases the resistance of such cells, and consequently the maintenance 

 of the species, is secured by the development of a protective wall of cells. This 

 is most frequently met with in zoogloaa- masses of bacteria. 



In other cases actual spore formation occurs. This, of course, takes place 

 not within the bacterial cell, since that would imply endospore formation, but by 

 a thickening of the membrane of the individual cell in question, which thereby 

 plays the part of a reproductive cell. This procedure is known as arthrospore 

 formation, since the spore detaches itself from the chain of moribund cells, encysts, 

 and becomes dormant until conditions are once more favourable for its germina- 

 tion, when the cell increases in length and subdivides in the same manner as the 

 vegetative form. 



The thickening of the cell membrane of the incipient arthrospore proceeds, 

 in many instances, to such an extent as to form spiny excrescences on the exterior 

 surface. This was observed by HA^SGIRG (I.) in two species of bacteria, viz., 

 M ycacanthococcus cellaris and Mycotetraedron cellare, found by him on the walls 

 of a cellar at the Castle of Pleissen, at Leipzig. The arthrospores of the latter 

 species, which are tetrahedral in form, exhibit at each of the four angles a spiny 

 thickening of the membrane 2 /u in length. 



The name arthrospore will be understood when it is remembered that this kind 

 of spore is met with particularly in the thread bacteria, from which it bcomes, as it 

 were, actually dismembered. Examples of this are exhibited by the Crenothrix 

 observed by Cohn, Cladothrix by Zopf, Leptothrix by Miller, and Streptothrix Fuer- 

 steri by GASPERINI (I.). The discovery of these organs in species of cocci, &c. 

 such as the urea bacterium found by JAKSCH (I.), in B. vernicosumby ZOPF (II.), 

 in Bacterium Zopjii by KURTH (1.). and so on was only a secondary matter. 



