12 PATHOLOGICAL MYCOLOGY. 



cases, as in the small portal spaces around the veins of the liver, they 

 may be found in very considerable numbers, with apparently very 

 little caseation. This caseation, however, advances rapidly. 



Digestive Ferments. 



10. Duclaux, as a result of his brilliant experiments, arrived at the 

 conclusion that bacteria act upon complex nitrogenous bodies much 

 as do some higher organisms (animals) by a process of true digestion, 

 and that in the process- of caseation the organic ferment secretes a 

 material which has much the same action upon milk as the diastase 

 secreted by the pancreas. 



Further, Pasteur supposes that no digestion can take place without 

 the presence of micro-organisms, by whose aid alone albuminoid sub- 

 stances are gradually transformed through a series of analytical pro- 

 cesses into comparatively simple and readily absorbed material, either 

 in the presence of oxygen, or in some cases where there is no free 

 oxygen present. Only when these soluble substances are formed can 

 there be any food material which the micro organism can apply to its 

 own use in carrying on its nutrition and development. Digestion 

 may therefore be looked upon as a process of fermentation, in which 

 the micro-organisms do not. utilise the whole of the material on which 

 they act, but set free a very large proportion, which may be utilised 

 by the organisation in which the process is carried on. The organ- 

 isms are various, and the products, though in the main similar, con- 

 tain, as a rule, a minute quantity of a specific substance, and it is this 

 specific substance which, in the pathogenic species, appears not only 

 to digest dead material, but also to prepare living or only slightly de- 

 vitalised tissues for digestion. 



In old tubercle masses the result of this process appears in the 

 form of caseous debris, from which all tubercle bacilli may have dis- 

 appeared, as they have selected what they required, and have ex- 

 hausted the materials which were necessary for their maintenance ; 

 but whilst doing this they have, by setting free their diffusible fer- 

 ment, prepared the- tissues in the immediate neighbourhood for the 

 reception of their progeny. In this way the process is continued and 

 extended. Continuing the analogy between the action of pathogenic 



