SPORE FORMATION 141 



certain well-marked changes occur in its protoplasm. This becomes 

 granular, and may even contain globules at an early stage. At the 

 same time the bacillus becomes distinctly broader, and paler in 

 substance. Meanwhile the globules increase in size, and in a few 

 hours' time become spores.^ The agencies which bring about sporu- 

 lation are not fully known. One theory obtaining considerable sup- 

 port may be expressed in the words of the late Professor Kanthack : 

 " There must always be the optimum of air, warmth, and nourish- 

 ment." Sporulation from this point of view is looked upon as the 

 zenith of the individual's life history — the highest stage in the vital 

 activity of a bacterium. In support of this theory- there are certain 

 facts. The formation of spores can be shown to take place before 

 the exhaustion of the favourable medium. B.filatnentosis is a simple 

 case in point, for it is able to produce spores on agar or potato 

 within twenty-four hours, and long before the medium is exhausted 

 or competition of other bacilli has had any effect Another 

 example is B. anthracis. This organism requires a sufficient 

 quantity of oxygen and warmth, and the absence of such favour- 

 able conditions inhibits sporulation. For example, by continued 

 cultivation in carbolised broth, or at an unfavourably high tem- 

 perature (42° C), this bacillus may permanently lose its property 

 of forming spores, and thus ijecome asporogenous. 



On the other hand, there is a second theory, which has the 

 support of a large number of observers, and which holds that sporula- 



' Koch found that spore formation in B. anthracis occurred in six hours. The 



spores may be situated in the middle of the bacillus (as in B. anthracis, B. acidi 

 butyrici, etc.), towards one end (Bacillus of Malignant CEdema) or actually 

 terminal {B. tetani). Those spores produced inside the capsule of the bacillus 

 are termed endospores. Hueppe has described the spores of certain streptococci 

 as arthrospores. The spores of yeast are termed ascospores. The spores of 

 all bacillary species possess, however, certain characters in common. They are 

 as follows. The spore is generally oval, though more spherical in the Hypho- 

 mycetes : it is bright and glistening in asi>ect ; it is often greater in diameter 

 than the bacillus giving rise to it ; its capsule is thicker and stronger than the 

 capsule of the parent bacillus ; and it is generally held that the contained 

 protoplasm is more concentrated, so to speak, than that of the bacillus. These 

 two last characters are of chief imp>ortance to us, for it is owing to them that 

 spores possess such marked power of resistance. Cohn has suggested that the 

 capsule of a spore is in reality a double envelope, an inner one of fatty and an 

 outer one of gelatinous nature, and it is owing to this that its resistance to heat 

 and desiccation is due. The protoplasm of the spore contains, of course, the 

 essential constituents of the mother cell. It is the method by which "the con- 

 tinuity of germ plasm " is secured in these lowly forms of life. Under favour- 

 able circumstances this spore-protoplasm will germinate into a new bacillus. 



