MESSMATES, MUTUALISTS, AND PARASITES 



77 



all directions through their tissues. Other fungi attack various 

 caterpillars, e.g. the silk- worm disease known as " muscardine " is 

 due to the Silk-worm Mould (a species of Cordiceps). A number 





Fig. 1071. A Ray-Animalcule (Arachnocorys circumtexta) with yellow cells (a), much enlarged 



of skin-diseases, such as ringworm and "barbers' rash" are caused 

 by parasitic plants of somewhat similar nature. 



But the most notable, and at the same time the smallest, of 

 the endoparasitic plants which attack animals are certain kinds 

 of bacteria, which may literally swarm within the 

 body, and give rise to a host of diseases, such as 

 relapsing fever, typhoid, leprosy, Asiatic cholera, 

 tuberculosis, diphtheria, anthrax, lock-jaw, and 

 bubonic plague. Some idea of the small size of 

 bacteria will be gathered from fig. 1073, or from 

 statements that make some appeal to the imagi- 

 nation. It is said, for example, that 250,000,000 

 individuals of the species associated with bubonic plague could 

 be crowded into the small space of a square inch. A number 

 more than six times as great as the population of the United 

 Kingdom at the last census. 



