80 ATLAS OF BACTERIOLOGY. 



2. Bacillus subtilis Colin. The membrane of the 

 growing spore bursts at the equator, the firm-walled 

 membrane of the spore adheres not infrequently to 

 the emerging young rod, even after it has grown into 

 a long filament. 



3. Bacillus sessilis Klein. The spore enlarges to a 

 marked degree, then ruptures at one pole, and from 

 the envelope of the spore grows a motionless filament, 

 to which the yellowish-green, contracted membrane 

 of the spore remains adherent for a very long time 

 (Fig. 10, 6). 



In old cultures of bacteria we almost always find 

 dead, often very queerly shaped bacterial cells (invo- 

 lution, degeneration forms), which are shown in Plate 

 40, Fig. V., and Plate 53, Fig. VI. These swollen, 

 bent, often unrecognizable forms stain poorly with the 

 ordinary reagents. The beginner will often regard in- 

 volution forms as the result of fouling ; 'the resort to 

 plate cultures will soon show whether we have to deal 

 with one or more forms of bacteria. 



B. The Chemical Composition of Bacteria. 



The body of bacteria consists in great part of water, 

 salts, and albuminoids ; * extractive matters which 

 are soluble in alcohol, and other bodies (triolein, 

 tripalmitin, tristearin, lecithin, cholesterin) which 

 are soluble in ether, are present in smaller amounts. 



* Albumin and salts may amount to ninety -eight per cent of 

 the dried bacteria (cholera vibrio), and on the other hand as 

 much as twelve per cent of carbohydrates may be present in the 

 membranes. Hellmich found a globulin in the bacterial albu- 

 min (Arch. f. exp. Path. u. Pharm., xxvi., 345). 



