PHYSIOLOGY 233 



parasitic or saprophytic, according to circumstances. What renders 

 the conduct of these lower organisms particularly striking is the 

 peculiarity possessed by many of them of not fully utilising all of 

 the organic matter at their disposal ; but, on the contrary, so 

 decomposing and disorganising the greater part of it by. their 

 fermentative activity that, while at first competitors are inhibited, 

 later their own development soon becomes restricted. When a 

 mould attacks an apple, it not only takes the small amount of 

 organic matter necessary for its sustenance, but at the same time 

 converts the whole apple into a soft decaying mass upon which the 

 fungus itself cannot exist. A considerable degree of heat is also 

 evolved in the course of these processes. The utilisation of the heat 

 produced in decomposing manure in making hot-beds is a familiar 

 practice. The heat produced by damp fermenting hay or raw cotton 

 may often become so great that in presence of inflammable gases 

 spontaneous combustion ensues. In germinating Barley an increase 

 in temperature of from 40 to 70 or more degrees has been observed. 

 The development of so much heat in this case is not due solely to 

 the respiration of the barley seeds, but according to CORN, to the 

 decomposing activity of a fungus (Aspergillus fumigatus). The 

 spontaneous combustion of raw cotton is, on the other hand, caused 

 by a Micrococcus. Coagulated albumen and thick gelatine are 

 rendered fluid by many Fungi and Bacteria, while the escaping gases 

 (carbonic acid, sulphuretted hydrogen, ammonium sulphide, ammonia, 

 etc.) show how far-reaching the decomposition is. In the same way 

 Penicillium brevicaule and other Fungi can liberate poisonous arsenical 

 gases when living on a substratum containing arsenic such as the 

 green pigments of wall-papers. In this way by Gosio's method 

 minute quantities of arsenic can be detected ( v2 ). It is by similar 

 processes of decomposition that dead organic matter becomes 

 thoroughly disorganised and rendered harmless. To the poisonous 

 bye-products formed by Fungi and Bacteria is due the severity of 

 many diseases which they produce in living organisms (potato 

 disease, wheat smut, cholera, typhus, diphtheria, anthrax, etc.). 

 By the possession or formation of substances, which react as specific 

 poisons upon the infecting Bacteria, plants, and particularly animals, 

 in turn protect themselves against the attacks of such micro-organisms. 

 It is due to a knowledge of this fact that the science of Therapeutics 

 has been enabled to cope more and more successfully with infectious 

 diseases. 



Fungi and Bacteria, in addition to the power, dangerous to themselves, of dis- 

 organising their own nutrient substratum by fermentation and putrefaction, also 

 possess the capability of making an unsuitable substratum suitable for their sus- 

 tenance. By means of inverting ferments they can convert an unsuitable cane-sugar 

 into an available grape-sugar, and by their diastatic ferments they are able to form 

 glucose and maltose from starch, and even from cellulose. 



