GAS FORMATION IN GAS GANGRENE 191 



wound. Consequently, whenever a wound becomes con- 

 taminated with soil, dirt, or dust containing manure, there is a 

 possibility of gas gangrene infection from Clostridium spores 

 in the manure particles. When soldiers fighting on cultivated 

 land become casualties, the probability of infection is high, 

 and gas gangrene becomes a major hazard of war. 



CI. welchii is a moderately proteolytic, highly fermentative 

 organism. When the viable organism begins to multiply in 

 the tissues surrounding an infected wound, the following 

 changes take place: — 



1. Liquefaction of the tissues 



This is due to the action of extracellular proteases attacking 

 tissue proteins and breaking them down to their constituent 

 amino-acids with the consequence that the tissue loses its 

 structure and " dissolves." In particular, CI. welchii excretes 

 a coUagenase, a proteolytic enzyme which hydrolyses the 

 collagen of muscle-fibres, including the sarcolemma, with the 

 result that the fibre-bundles disintegrate. 



2. Production of gas 



There are two main sources of the gas which appears in the 

 infected tissue. First, the organism is able to ferment muscle 

 glvcogen with the production of hydrogen, carbon dioxide, 

 acetic and butyric acids, and other products. However, if 

 CI. welchii is grown in the presence of meat protein freed from 

 glycogen, gas is still produced in large quantities. This gas 

 is produced by the deamination of certain amino-acids, 

 especially serine, with the liberation of Hg, CO2, NH3, etc. 

 (see p. 167). The action of the proteases on tissue protein 

 assures a steady supply of free amino-acids to act as source 

 of gas in this way, 



3. Production of histamine 



CI. welchii, when growing in an acid medium, produces 

 histidine decarboxylase. Histidine is liberated from tissue 

 protein by the action of proteases, and the fermentation of 



