IMMUNITY AGAINST MICROBES. 99 



Immunity against Microbes. 



By 

 H. Armand Ruffer, M,A»i ]fI.D.(Oxon.) 



Part I. — A. 



When examining the microscopic world actively growing in 

 various infusions, we are often able, says MetschnikoflF/ " to 

 follow with our eyes the struggle taking place between the 

 representatives of the Flora and Fauna of microbes. Many 

 unicellular animals, such as Amoebae and other Rhizopoda, as 

 well as flagellated and ciliated Infusoria, feed on various 

 bacteria, devour them in great numbers, and take them into 

 their protoplasm in order to extract from them the necessary 

 nutritive material. Small Monads in the course of a few 

 minutes take into their interior Leptothrix filaments ten times 

 longer than they are themselves.^' It is a very old observation 

 that Amoebae and other Protozoa seize dead particles, and, 

 after extracting the nutritive material contained in these, reject 

 the remainder. 



According to Metschnikoff,^ there is no proof that the cells 

 forming the ectoderm of some lower animals — sponges for in- 

 stance — have the power of taking solid substances into their 

 interior. The same observer, however, has shown that the 

 ectodermic cells of other Metazoa have that power. If, for 

 instance, a small quantity of powdered carmine or indigo be 

 added to water containing Plumularia (Plumularia setacea 

 or others), some of the carmine or indigo finds its way into the 

 ectoderm of the Nematocalyces. These organs send out 



1 'Ann. de I'Institut Pasteur,' 1887, p. 321. 



2 ' Arbeiten aus dem Zool. Institut in Wien u. Triest,' vol. v, 1884. 



