13° PRACTICAL BACTERIOLOGY. 



venient benches are those made of simple glass plates, 

 whose ends are bent back ; those which are made of 

 long thin pieces cemented together are not so good, 

 for they are difficult to sterilise, and also are liable 

 continually to fall to pieces. 



The first thing to be noticed in the developing spore 

 is a slight change in its refractive power ; it becomes 

 less glistening and appears to increase very slightly 

 in circumference. Gradually the membrane, which 

 originally was of equal thickness all over, becomes 



I'm. 8. 



weaker in parts, being thinner at the sides, whilst at 

 the poles it retains its original thickness. Finally 

 it seems to disappear entirely on one side, but careful 

 examination shows a delicate border, which is some- 

 what arched forwards. At last the membrane gives 

 way at this point, and the young rodlet emerges one 

 end foremost ; it soon grows to its full size, and after 

 from half an hour to an hour begins to divide. 



Sometimes, however, the rodlet cannot get oat of 

 its spore case so easily ; it cannot manage to intro- 

 duce either of its ends through the aperture, and thus, 

 as it continues to grow, has to force its way out back- 

 wards, so that at last it is curved like a horse shoe. 



