THE STORY OF THE BACTERIA. 6 1 



however, been done recently on this subject, 

 and a great many animal experiments made, 

 until now we know not only that blood poison- 

 ing but abscesses, erysipelas, and many other 

 less serious inflammations are caused by bac- 

 teria. We have found out, furthermore, that 

 there are two particular species which cause 

 the trouble in the great majority of cases. 



Both of these bacteria are little balls or 

 micrococci. One of them, as it grows, tends 

 io form chains, and so is called Streptococcus ; 

 the other tends to group itself in clusters a 

 little like a bunch of grapes, and so is called 

 Staphylococcus. 



Now, it has been further found that these 

 two forms of bacteria are quite abundant 

 where people are gathered, mostly in dirty 

 places ; sometimes where the healthy, but espe- 

 cially where sick people are crowded together, 

 as in hospitals, They are found in small num- 

 bers floating with the dust in the air, where 

 dust lodges, and often in the mouths and on 

 the clothing of the people themselves. 



It is thus evident how the wound diseases, 

 such as blood poisoning, can come about, for 



