ACTION ON TISSUES— ABSCESS. 7 



to all parts of the tissues of its host, carrying its irritative pro- 

 perties with it, and producing a general disease which puts to the 

 test the vitality of the affected organisation as a whole. To this 

 class belong the organisms which produce the very varied symptoms 

 met with in the specific fevers. In any of these cases the direct rela- 

 tion of the micro-organism to the tissue elements of its host is probably 

 a dual one. In the first place, the mere fact of its presence as a 

 foreign body amongst the tissues gives it the character of a mechanical 

 irritant. In addition, it may be that one of its vital peculiarities is to 

 evolve an irritating product or ptomaine, which, in virtue of its 

 chemical constitution, either irritates the adjacent tissues, in which it 

 may produce a local necrosis, or, as in certain cases, its poisonous 

 effects are spread through the whole of the tissues of the body. It 

 may be that there is, in addition to these two methods of irritation, 

 a more subtle influence exerted by the organism upon the tissue 

 elements of its host, a physico-chemical or molecular reaction occur- 

 ring between the two, which gives rise to local or to general changes. 



Acute Abscess — Tubercle. 



6. The marked difference which exists, and which is much greater 

 than at first sight appears, comes into bold relief if the stages in the 

 formation of an acute abscess are observed on the one hand, and those 

 of tubercle formation on the other. In the case of an acute abscess, 

 an indurated mass of tissue is first noticed. If this be punctured, no 

 pus escapes ; the tissue reaction has not yet reached the stage of pus 

 formation, but a drop of perfectly clear serum exudes from the centre 

 of the mass. On examination this is found to consist of a few lymph 

 cells and immense hosts of chain or cluster-forming micrococci float- 

 ing in the lymph. If this puncture be repeated in twenty-four hours 

 pus is found to be present in small quantities, loaded with the same 

 organisms. If repeated punctures be made at intervals, an increased 

 quantity of pus is found each time, and the organisms from the com- 

 mencement of pus formation begin to decrease, till, in an old abscess 

 of some weeks' standing, no living micro-organisms are present; but 

 the pus is found to contain dead micrococci, not readily recognisable, 

 as they are partially broken down and take on staining reactions very 



