383 



worms is merely an accompaniment, not an effect of the phenomenon ; 

 and that heat and electricity act merely like other stimuli upon the 

 vital powers of the animal. 



Observations and Experiments on Pus. By George Pearson, M . D. 

 F.R.S. Read July 5, 1810. [Phil Trans. 1810,;?. 294.] 



The author prefaces the account of his experiments and observa- 

 tions on the nature and properties of purulent fluids, by an etymo- 

 logical disquisition concerning the origin of the word Pus, and the 

 various senses which philologists may discover for the word irvos, be- 

 sides the distinct signification given to it by Hippocrates, of a thick, 

 white, inodorous, uniformly smooth fluid, which is contained in an 

 abscess. From the etymology, Dr. Pearson next proceeds to the 

 history of the several opinions that have been entertained respecting 

 the formation of purulent matters, and of the characters by which 

 different persons have endeavoured to distinguish real pus, from such 

 purulent fluids as ought rather to be considered as modifications of 

 mucus. Since nothing appears to have been added since the date of 

 Mr. Home's dissertation on pus, which was written in the year 1798, 

 Dr. Pearson's history concludes with an outline of Mr. Home's ac- 

 count of the nature of pus. According to him, pus is composed of 

 globules swimming in a transparent aqueous fluid. The globules, on 

 which its opacity depends, are formed subsequently to the secretion 

 of the transparent fluid. They are not soluble in cold water, like 

 those of blood, but are decomposed by boiling water ; and the fluid 

 in which they swim is not coagulable by heat, as serum, but is co- 

 agulable by sal-ammoniac, which does not coagulate serum. 



Dr. Pearson's examination of pus is divided into six sections, of 

 which the first treats of the simple and obvious properties ; and he 

 distinguishes four different kinds of pus. 



1. The cream-like and equally consistent. 



2. The curdy of unequal consistence. 



3. The serous, or thin kind. 



4. The thick, viscid, or slimy. 



Of course, as he examines, under the name of pus, fluids so dif- 

 ferent from each other, he obtains results which differ accordingly 

 in the qualities and quantities of their ingredients. 



In the second section the agency of caloric is observed. 



According to the author, all kinds of pus are coagulated between 

 160 and 165 of Fahrenheit. By continued heat the water is eva- 

 porated, and there remains a dry brittle mass, amounting to about 

 one seventh or one eighth of the original weight. By exposure to 

 greater heat in a crucible of platina, the greatest part of this resi- 

 duum was consumed, and there remained only the salts of the serum 

 fused together, and amounting to -j-rTrth, -j-^dth, or 7 ^-o-dth, of the 

 original quantity of pus employed. 



These, says the author, consisted chiefly of muriate of soda, phos- 

 phate of lime, potash, with strong indication of carbonate of lime, 



