Dec. 2, 1908.] Agricultural Gazette of N.S.W. 1025 



down as far as the air can enter. A<^ain, some fresh sihige juice, which gave 

 up 38 per cent, of its nitrogen on treatment with nitrous acid, was allowed 

 to become mouldy ; after three months only 18 per cent, was set free. 



The disappearance of non-protein, and the formation of protein, indicates 

 that the moulds and other organisms have utilised the simpler substances as 

 food, and built them up into complex cell constituents. A similar change is 

 known to take place when farmyard manure is stored. 



The chemical eflfects following on the admission of air can be ascribed to 

 the course of respiration in the cell, which now remains normal, so that 

 butyric and acetic acids are no longer formed in quantity, and to the 

 development of mould, which appears in the black, decomposed layei's at the 

 top of the silo as far as oxygen can get in, but not lower down. Indeed, the 

 absence of mould is characteristic of good silage, though it is very ditficult 

 to explain. Penicillium is reckoned among the hardiest forms of life. It 

 seems able to grow almost anywhere, and to tolerate bodies that would be 

 fatal to most other organisms, yet it cannot grow in the silo, and at a certain 

 distance down it stops absolutely short. On the dividing line, Avhere the 

 black, mouldy layer ends and the good silage begins, the author has often 

 found pieces of maize 1 inch long, one end of which was strongly acid and 

 free from mould, while the other was alkaline and had a growth of Penicil- 

 lium. It would appear that there is some actual inhibiting agent produced 

 in the silo when oxygen is absent and not formed when oxygen is present, 

 though no doubt the absence of free oxygen in the silo is also a cause why 

 mould does not develop. 



The Course of the Process in the Silo. 



Putting together our results, it is possible to sketch out fairly completely 

 what happens in the silo. When the cells are put in they are alive and their 

 vital functions continue. Respiration goes on and sugar, ikc, is used up, 

 but in absence of air oxidation is not complete, and intermediate bodies — 

 alcohol, acetic acid, butyric and other acids— are formed, in addition to carbon 

 dioxide and water. The tryptic enzymes of the cell act on the protein 

 forming the usual hydrolytic products — amino acids, diamino acids, ttc. : 

 from the nucleo-proteins purin bases are produced in addition. The heat 

 developed during these processes cannot be dissipated, as it usually is in the 

 living plant by the evaporation of water, because water vapour cannot 

 escape from the silo ; instead, it raises the temperature of the mass. Respira- 

 tion is accelerated by the increased temperature, but, as no more material is 

 being elaborated, and only decomposition is taking place, the process soon 

 comes to an end. The cell then dies for want of more substance to break 

 down ; it loses its turgidity and becomes Haccid, causing the mass to settle 

 down. The temperature also steadily falls.i The decomposition of the 

 protein, which had also been accelerated by the rise in temperature, can 

 continue even after the cell is dead, because the enzymes when once formed 



1 The maximum of 33° to ST C (91-4° to 9S-6° Fahr.) observed in the Wye silo was 

 always reached in about five days ; there was then a slow but regular fall. 



