NUTRITION OF PARASITES AND SAPROPHYTES 13$ 



excretes the diastase, which acts on the starch in the rice, convert- 

 ing it into sugar. Taka diastase is very powerful and abundant. 

 It is extracted from the fungus and sold for medicinal purposes. 

 It is used by people who have weak digestion to aid in the digestion 

 of starchy foods. Many of the plant diastases are very powerful; 

 a small quantity can dissolve a great deal of starch without in 

 the least diminishing its activity. Recent investigations tend to 

 show that a diastase (called zymase) is produced by the yeast 

 plant, which is the active agent in the alcoholic fermentation of 

 sugar, and it would appear that there is not such a great differ- 

 ence between organized and unorganized ferments, for it may be 

 found that the active principle in all so-called organized ferments 

 is an unorganized ferment or enzyme. Oil products in seeds, etc., 

 are rendered available for plant food by a ferment called lipase, 

 cellulose (in some seeds) by a ferment called cytase, proteid 

 bodies by ferments called proteases, and albuminoids by a tryptic 

 ferment. 



BACTERIA. 



220. The bacteria are very minute plants, some of them the 

 smallest known organisms. Like the fungi they lack chlorophyll, 

 and derive their carbohydrate 

 food from living or dead organ- 

 isms or from organic matter, 

 since they are not able them- 

 selves to fix carbon from the 

 carbon dioxide of the air ex- 

 cept in a few forms like the 



nitrite and nitrate bacteria (see threads, unstained roS, and stained rodsSowing 



i \ rr>i n cilia; B, Bacillus tetani, the tetanus or lockjaw 



paragraph 20O). 1 hey USUally bacillus, found in garden soil and on old rusty 



, r i n ,! nails. Spores in clubshaped ends. C, Micro- 



COnSlSt of a Single Cell With coccus; >, Sarcina; E, Streptococcus; F, Spiril- 



cell wall enclosing the proto- lum " (Aftei 



plasm. In form they are rod-like (Bacillus, Bacterium), thread-like 

 and formed of many rod-like segments (Beggiotoa), in the form of 

 a screw or spiral (Spirillum), spherical and single (Micrococcus), 

 or a number of spheres in a chain (Streptococcus), or with the 

 spheres in groups of four (Sarcina). They usually multiply by 



