IMMUNITY AGAINST MICROBES. 421 



bacilli. The fluid, as a rule, is somewhat turbid, owing to the 

 presence of wandering cells in fairly large numbers. These 

 amoeboid cells belong to the small variety (microphages), and 

 are either uni- or multi-nucleated. The nuclei possess hardly 

 any intra-nuclear network, and are surrounded by a small 

 amount of protoplasm only. Many of these cells contain 

 bacilli, some in enormous numbers, as many as ten micro- 

 organisms being occasionally enclosed in one cell. The micro- 

 organisms in the liquid show no signs of degeneration, whilst 

 some of the bacilli contained in the amoeboid cells have clearly 

 undergone a process of digestion. Floating in the liquid are 

 seen remnants of the dried blood used for the purpose of 

 inoculation. 



On microscopical examination the free aspect of the abscess- 

 wall is covered everywhere by an enormous number of bacilli, 

 lying free in the coagulated exudation fluid, staining in a 

 perfectly normal manner, and showing to all appearances no 

 traces of degeneration. 



The abscess-wall itself consists of an innumerable number of 

 small migrating cells. Some of these amoeboid cells have but 

 one single nucleus ; others contain two, three, or four nuclei. 

 In many the nucleus has the triradiate aspect found in other 

 inflammatory conditions — for example, pneumonia. The 

 amount of protoplasm round the nucleus is very small as a 

 rule. Close to the free surface of the abscess-wall these cells 

 are pressed together in enormous numbers, and so closely 

 packed that the contours of each are scarcely to be recognised. 



In the deeper regions of the abscess-wall the cells are massed 

 together less closely. The muscular tissue around contains 

 within its meshes and between its fibres a large number of 

 small round migrating cells. The latter are met with even in 

 places where not a single bacillus is to be seen. Here and 

 there, especially in the deeper strata of the abscess-wall, a few 

 cells occur which are larger, have a single, clear, vesicular 

 nucleus, with a well-marked intra-nuclear network, surrounded 

 by a large amount of coarse protoplasm, and not infrequently 

 contain in their interior remnants of degenerated bacilli and 



