10 BACTERIA 



by many authorities to be different species, owing to their 

 different effects. Morphologically all the streptococci are 

 similar, though a somewhat abortive attempt was once made 

 to divide them into two groups, according to whether they 

 were long chains or short. As a matter of fact, the length 

 of streptococci depends in some cases upon biological prop- 

 erties, in others upon external treatment or the medium of 

 cultivation which has been used. Sometimes they occur as 

 straight chains of only half a dozen elements ; at other times 

 they may contain thirty to forty elements, and twist in 



SARCINA 



various ways, even forming rosaries. The elements, too, 

 differ not only in size, but in shape, appearing occasionally 

 as oval cells united to each other at their sides. The fourth 

 form is constituted by the micrococci being arranged in 

 masses like grapes, the staphylococcus (ar&q>i$k{s 9 a bunch of 

 grapes). The elements are often smaller than in the strep- 

 tococcus, and the name itself describes the arrangement. 

 There is no matrix and no capsule. This is the commonest 

 organism found in abscesses, etc. The sarcina is best 

 classified amongst the cocci, for it is composed of them, in 

 packets of four or multiples of four, produced by division 

 vertically in two planes. If the division occurs in one plane, 

 we have as a result small squares of round cells known as 



