92 SCIENCE AND PRACTICE OF DAIRYING. 



those smallest of living growths known under this name, belong to 

 the lower fungoid kind, which in their turn belong to the crypto- 

 gams. The lower fungi can be divided into fungi proper (moulds), 

 budding fungi (yeasts), and fission fungi (bacteria). Their function 

 in nature is to set up in the lifeless higher organic bodies a con- 

 tinuous process of disintegration and decomposition, and finally to 

 mineralize them that is, to convert them into water, carbonic 

 acid, ammonia, nitric acid; in short, to change them into simple 

 inorganic compounds, from which the entire higher plant world 

 builds up its organic material. 



According to the special phenomena which occur in such de- 

 composition processes, according to the nature of the transition 

 products formed, and according to the nature of the organisms 

 which effect them, the process is called decomposition, putrefaction, 

 or fermentation. No decomposition can take place without the 

 presence of moulds or budding fungi. The characteristic putre- 

 factive processes are essentially caused by fission fungi, and in the 

 production of fermentation, budding fungi (beer and wine fermen- 

 tation), as also acetic, lactic, butyric, and urea ferments, also take 

 part. In the development of their special action the different kinds 

 of the lower fungi exhibit different striking phenomena. Some 

 yield colours, others cause phosphorescence, while others again 

 produce liquids in which grow thick and slimy chemical ferments 

 (enzymes), causing the production of odours and smells or the 

 production of substances, which exercise on human and animal life 

 an extremely poisonous action (ptomaines and toxalbumins). But 

 the action of the lower fungi is not limited to lifeless organic bo lies. 

 There are numberless kinds which are able to take possession of 

 living organisms, some of which not merely exist in living plants 

 and animals or inside the human body, and as parasites feed upon 

 their hosts in exceptional cases, but there are others which threaten 

 them with degeneration and death. 



The lower organisms possess interest for us in this connection 

 in a threefold manner. For example, they are quite indispensable 

 for the continuance of all living nature, inasmuch as they cause 

 putrefaction and decomposition of dead organic matter, and render 

 possible the development and the existence of the entire higher plant 

 and animal world. Of the greatest utility are those by whose action 

 the growth of certain kinds of our cultivated plants is assisted, and 

 those which act in the preparation of certain foods as bread and 



