PATHOGENIC BRCTERIA. 283 



The cells of the tissues surrounding the necrotic area are 

 mingled with large numbers of polynuclear leukocytes, which 

 enclose the area of irritation. 



The nuclei of the cells near the center of the abscess are fre- 

 quently broken up into a number of small fragments, which in 

 dicates the commencement of their destruction. In sections 

 through small abscesses it is possible, by means of a double 

 stain of carmine, followed by Gram's method, to bring out 

 the histological character of the tissue, and at the same time 

 to stain the common .phyogenic bacteria, which are usually 

 found near the center of the abscess in large numbers, even 

 making masses visible with a low power of the microscope. 

 It is often possible by this method to demonstrate masses of 

 micrococci filling up the lumina of capillaries in which they 

 are lodged as emboli. 



The production of pus in the center of the abscess is due to 

 the liquefaction of the necrotic tissue, which apparently results 

 from the action of some peptonizing ferment. In the liquid 

 thus formed immense numbers of the polynuclear leukocytes 

 are found floating, and they constitute the greater part of the 

 so-called pus-cells. The nuclei of these cells are obscured by 

 clouds of extremely fine granules. The granules are of an 

 albuminoid nature, and are dissolved by acetic acid, when the 

 nuclei become visible. The nuclei generally consist of three, 

 four, or five more portions. Pus-cells may contain fatty 

 granules; sometimes the cells are necrotic; sometimes living 

 leukocytes may be present. The pus-cells may also contain 

 bacteria. The presence of the fine albuminoid granules in the 

 pus-cells is to be counted as a degenerative change. Although 

 it is possible to produce suppuration experimentally by the 

 introduction of sterilized irritants, such as croton oil, into the 

 tissues of animals, in all cases met with in practice suppuration 

 is due to the action of pyogenic bacteria. 



Specimens of pus will nearly always be found to contain 



