QUESTION OF ARTHROSPOROUS BACTERIA. 7 



at a temperature above the limit at which it grows best, not 

 only are no spores formed, but the species may lose the power 

 of sporulation. Furthermore, in the case of bacteria preferring 

 the presence of oxygen for their growth, an abundant supply of 

 this gas may favour sporulation. Most bacteriologists are, 

 however, of opinion that when a bacterium forms a spore, it 

 only does so when its surroundings, especially its food supply, 

 become unfavourable for vegetative growth ; it then remains in 

 this condition until it is placed in more suitable surroundings. 

 Such an occurrence would be analogous to what takes place un- 

 der similar conditions in many of the protozoa. Often sporu- 

 lation can be prevented from taking place for an indefinite time 

 if a bacterium is constantly supplied with fresh food (the other 

 conditions of life being equal). The presence of substances 

 excreted by the bacteria themselves plays, however, a more 

 important part in making the surroundings unfavourable than 

 the mere exhaustion of the food supply. A living spore will 

 always develop into a vegetative form if placed in a fresh food 

 supply. With regard to the rapid formation of spores when the 

 conditions are favourable for vegetative growth, it must be 

 borne in mind that in such circumstances the conditions may 

 really very quickly become unfavourable for a continuance of 

 growth, since not only will the food supply around the growing 

 bacteria be rapidly exhausted, but the excretion of effete and 

 inimical matters will be all the more rapid. 



We must note that the usually applied tests of a body de- 

 veloped within a bacterium being a spore are (i) its staining 

 reaction, namely, resistance to ordinary staining fluids, but 

 capacity of being stained by the special methods devised for 

 the purpose {vide p. 106); (2) the fact that the bacterium 

 containing the spore has higher powers of resistance against 

 inimical conditions than a vegetative form. It is important 

 to bear these tests in mind, as, in some of the smaller bacteria 

 especially, it is very difficult to say whether they spore or not. 

 There may appear in such organisms small unstained spots the 

 significance of which it is very difficult to determine. 



The Question of Arthrosporous Bacteria. — It is stated by Hueppe that 

 among certain organisms, e.g. some streptococci, certain individuals may, 

 without endogenous sporulation, take on a resting stage. These become 

 swollen, stain well with ordinary stains, and they are stated to have higher 



