66 BACTERIA IN DAILY LIFE 



primitive forms of vegetable existence with which 

 we are acquainted, i.e. bacteria. In fact, we have 

 found out that if we wish to keep our microbial 

 nursery in a healthy, flourishing condition, we must 

 carefully banish all sources of light from our culti- 

 vations, and that a dark cupboard is one of the 

 essential requisites of a bacteriological laboratory. 

 That light had a deleterious effect upon micro- 

 organisms was first discovered in this country by 

 Messrs. Downes and Blunt, and their investigations 

 led Professor Tyndall to carry out some experi- 

 ments on the Alps, in which he showed that flasks 

 containing nutritive solutions and infected with 

 bacteria when exposed in the sunshine for twenty- 

 four hours remained unaltered, whilst similar vessels 

 kept in the shade became turbid, showing that in 

 these the growth of bacteria had not been arrested. 

 In these experiments mixtures of micro-organisms 

 were employed, and the interest elf the French 

 investigations which followed lies in the use of 

 particular microbes notably the anthrax bacillus 

 and its spores,* Roux demonstrating very conclu- 

 sively that the bacillar form was far more sensitive 



* In the interior of some bacilli there appears a round or oval 

 body, having a very bright and shining lustre, which is known as a 

 spore> and plays a most important part in the propagation of many 

 kinds of bacilli. These spores are capable of resisting many hard- 

 ships, which would be immediately fatal to the parent bacilli from 

 which they have sprung. 



