SARCINA. 153 



there is a group which exhibits an inverting action on a pure 

 saccharose solution, but loses this property when yeast- 

 water is added. 



Wortmann in 1882 began some experiments on the diastatic 

 action of bacteria, and used for this purpose drops of bacterial 

 liquids on rotten beans or potatoes. He proved that in this 

 mixture species were present which can bring about the same 

 changes in starch paste and in soluble starch as the diastase 

 of the higher plants can do. The bacteria only exert action 

 on starch when no other available carbohydrate is present 

 (e.g., sugar or tartaric acid). This was established by means 

 of experiments with inorganic nutritive solutions. Krabbe 

 showed that the presence of peptone increased the formation 

 of diastase. Fermi proved that this enzyme was present in 

 different Streptoihrix species, and found that the formation of 

 diastase was prevented when the bacteria were cultivated on 

 substrata free from albuminoids. Pfeffer and Katz observed 

 a rich formation of diastase in Bac. Megatherium ; by the addi- 

 tion of saccharose or maltose to the nutrient the diastatic 

 activity was considerably reduced. Garbowski observed the 

 enzyme in his detailed researches on Bac. luteus. The action 

 is brought out most strongly by inoculating on an inorganic 

 nutritive liquid, together with starch solution. 



Bac. vulgar is and Bac. prodigiosus are amongst the organisms 

 containing proteolytic or peptonising enzymes. The latter, 

 which belongs to the group of colour-forming bacteria (the 

 " Bleeding Host ") forms very short motile rods in weakly 

 alkaline substratum, but longer rods and filaments in weak 

 tartaric solutions. These albuminoid-digesting bacteria play 

 an important part in nature, in the decomposition and suc- 

 cessive building up of organic substances. The anaerobic 

 species appear to be particularly active ; for example, Bac. 

 putrificus, which forms long motile rods, with spore-formation 

 at their swollen ends. 



9. Sarcina. 



The name Sarcina is given to the spherical bacteria (Coccus], 

 which are motionless, and divide in all three planes. Under 

 favourable conditions of growth, and especially in liquids, 



