86 THE SECRETIONS: 



by acetic acid, but is rendered white and opaque by the addi- 

 tion of nitric acid: the action of heat likewise renders it turbid, 

 and coagulates a considerable quantity of albumen, which sepa- 

 rates in the form of flocculi. 



Infusion of galls and basic acetate of lead cause dense pre- 

 cipitates ; in fact, the addition of the former sometimes com- 

 pletely thickens the fluid. 



The quantity of albumen is therefore much larger than in 

 simply diseased mucus. 



Pus. 



Violent irritation of the mucous membrane may produce 

 suppuration and cause a secretion of pus in place of the or- 

 dinary mucous secretion; thus it appears that the formation 

 of pus is dependent on the very same process which, when 

 acting with less intensity, first increases the secretion of mucus, 

 and subsequently renders it abnormal. Pus, however, also 

 forms in other and distinct parts of the body, after pre-existing 

 congestion and inflammation, as for instance in cellular tissue, 

 skin, muscular tissue, &c., and appears to differ both in its phy- 

 sical and chemical characters in accordance with the seat of 

 its formation and the length of time that it has remained in 

 the organism. 



Genuine pus usually occurs as a rather thick fluid, viscid, 

 but capable of separating in drops, somewhat like cream, of a 

 whitish-yellow, yellow, or greenish-yellow colour, and of a faint 

 but not disagreeable animal odour. It may be slightly acid, 

 slightly alkaline, or neutral ; when mixed with water it sinks 

 rapidly to the bottom, but on stirring, it forms an emulsive 

 fluid, from which a sediment of pus- corpuscles is soon again 

 deposited. 



When examined under the microscope, pus appears (like 

 mucus) to consist of a clear fluid in which small, round, and 

 occasionally oval corpuscles are swimming, the quantity of which 

 seems to be in a direct ratio with the thickness of the pus. 

 Pus- and mucus-corpuscles so closely resemble each other, that 

 no distinctive mark, founded either on their form or on their 

 chemical relations, has hitherto been discovered. The size of 

 the corpuscles is nearly the same ; in tough pus they are some- 



