ENZYMES OR FERMENTS 37 



up with the living protoplasm are spoken of as the endoenzymes 

 us opposed to the soluble enzymes or ferments which are secreted 

 by the living cells. The two types, however, are difficult to 

 separate and the one set grades into the other. Macfadyen, 

 Morris and Rowland devised a method of cutting minute organ- 

 isms in mass and thus breaking down the cells more perfectly 

 than had been done before, and with yeast they succeeded in 

 isolating not only a powerful zymase but other endoenzymes 

 as well, these including maltase, invertase, endotryptase, rennin, 

 and traces of two others, all of which must be present in the 

 normal protoplasm of living yeast cells, although perhaps not 

 in the form of active ferments but probably in an inactive form 

 to which the general term zymogen is given. 



B. BACTERIA 



Bacteria is a term used to designate a great group of minute 

 forms of life intermediate, like yeast, between chlorophyll- 

 bearing plants and animals. They occur almost everywhere; 

 abundantly in the atmosphere accompanying dust particles; 

 frequently in fresh and salt water; abundantly in the digestive 

 tract of all kinds of animals. They abound in the upper layers 

 of the soil and in exposed fluids containing dead animal or 

 vegetable matter. Some types produce disease in man and 

 other animals whence they are popularly known as germs or 

 microbes or parasites. Many of them, on the other hand, are 

 positively useful physiologically, in the functional activities of 

 higher animals, and economically and commercially in trans- 

 forming organic matter into simple salts (nitrites, nitrates, etc.) 

 or in the manufacture of various food stuffs (vinegar, butter, 

 cheese, etc.). 



Morphology of Bacteria. Bacteria are the smallest of the 

 k:nown organisms. Some types placed end to end would 

 require 25,000 to cover a linear inch, and the line would be too 

 fine to be seen; 50,000 such lines side by side would cover a 

 square inch. Other types are larger, varying from 2/x to 6o/z 

 in length. 1 



1 A ju (micron) equal 1-25,000 of an inch. 



