CHAP. VL] PUS. 239 



allowing their nuclei to be seen, and the latter may then be readily 

 stained with magenta or even with carmine. 



As usually obtained, pus corpuscles resemble dead rather than 

 living colourless blood-cells, as evidenced by the absence of contrac- 

 tility. 



Pus corpuscles are liable to undergo certain changes, of which the 

 most common is fatty degeneration ; the cells then contain a number 

 of highly refracting, obviously fatty, granulations ; at a more ad- 

 vanced stage, the cells break down and the fatty granulations thus set 

 free float in the pus-serum. 



Nature of The liquid portion of pus pus serum resembles 



PUS and the liquor sanguinis and the normal transudations very 



origin of Pus closely, and, doubtless, is in great part, in the first 

 cells. instance, a transudation from the blood. With regard 



to the pus corpuscles, they are, for the most part, either colourless cells 

 of the blood which have wandered through the capillary walls into 

 the extra- vascular spaces, or the offspring of such emigrated cells ; in 

 some cases, however, it is possible that the pus cells are derived from 

 the normal cells of the tissues amongst which they are found, 

 especially from epithelial and endothelial cells. 



SEC. 2. THE Pus SERUM. 



The liquid in which the pus corpuscles are suspended may be 

 separated in an unmixed condition by filtration ; the process is, how- 

 ever, a tedious one ; it may be obtained more readily, by mixing pus 

 with an equal volume of a solution of one part of sodium sulphate in 9 

 parts of water arid then filtering; the liquid which passes through the 

 filter is then a mixture of pus serum and solution of sodium sulphate. 

 Doubtless the separation would, in either case, be much facilitated by 

 the use of the centrifugal apparatus. 



Pure pus serum is a turbid liquid which has a brownish tint 

 when examined by reflected light, whilst by transmitted light thin 

 layers appear of a yellow colour. Its reaction is usually alkaline. 



Proteid Pus serum contains substantially the same proteid 



matters of matters as blood serum, viz. serum-globulin and serum- 

 pus serum. albumin ; the former is partly precipitated by C0 2 , but 

 may, as in the case of blood serum, be completely precipitated by 

 saturating with magnesium sulphate. 



Extractive These consist of a mixture of neutral fats, cholesterin, 



matters and of a derivative of glycerin-phosphoric acid. This 



soluble in derivative is, according to Hoppe-Seyler, probably the 



same as lecithin, the phosphorized proximate principle of 



the yolk of egg; according to Fischer 1 it is protagon. The matter is yet 



1 Fischer, Centralblatt f. d. med. Wissenscliaften, 1865, p. 225. 



