168 



VETERINARY PATHOLOGY. 



Histologically, pus is composed of pus cells, i. e., leucocytes 

 (the most of which are necrotic, though some of them may pos- 

 sess vitality), shreds of necrotic tissue and tissue cells (the type 

 of which depends upon the tissue affected), usually pyobacteria 

 in varying numbers (many of them being included in the pus 

 cells) and liquor puris (the plasma or fluid portion of the exu- 

 date and the fluid resulting from the solvent action of the vari- 

 ous ferments). Animal microparasites are found in the pus re- 

 sulting from their activity. Practically all of the pus cells are 

 derived from polymorphonuclear leucocytes, and are usually the 

 neutrophile varietv, there being only an occasional mononuclear 

 leucocj'te. Extensive nuclear fragmentation and parenchyma- 

 tous and fatty degeneration of the cell protoplasm are evident in 

 most pus cells, indicating that they have undergone necrosis. 

 Degeneration or necrosis are also present in the fixed tissues of 

 the suppurative areas. The pus found in acute abscesses or dis- 

 charging from granulating wounds is usually a creamy fluid, 

 yellowish in color. Sanious pus is a reddish fluid resulting from 

 an admixture with blood. Ichorous pus is an acrid, corrosive 

 fluid that excoriates the tissues it contacts. Muco-pus and bero- 



Fi.i^. 101. — Drawing of a pus smt'ar from a case of strangles, showinp: the organism 

 arranged in chains — th'- Streptococcus p.\ogenes c<nii. 



