148 EXUDATIONS. 



separated by filtration from the intercellular fluid, and they also 

 render indirect determination more difficult, in consequence of 

 their possessing a far less sinking capacity than the blood- 

 corpuscles ; the cyto'id corpuscles of the blood remain, however, 

 suspended like those of pus. After standing for some time, the 

 pus-corpuscles begin gradually to sink ; the pus is then, however, 

 generally changed in character, and the cytoi'd corpuscles exhibit 

 more distinctly the nuclei which had previously been scarcely 

 discernible. The serum of the pus has a less decided alkaline re- 

 action than that of the blood ; indeed sometimes it is acid, and when 

 placed in a vacuum, this kind of pus commonly evolves sulphuretted 

 hydrogen gas. We cannot, therefore, regard the serum of the 

 pus, which is accessible to investigation, as a perfectly pure object. 

 But although this condition of the pus-corpuscles must be 

 regarded as the principal obstacle in the way of a rational 

 investigation of this fluid, there are not wanting other causes 

 which very frequently render the object unsuited for a conclusive 

 analysis; amongst these we may especially enumerate the frequent 

 occurrence of blood in pus, that is to say, particles of fibrin and 

 blood-corpuscles, as well as the elements of newly formed, or 

 recently destroyed tissues. Such fluids would, at all events, be 

 unsuited for analyses, from which we might wish to draw con- 

 clusions regarding the special character of the pus, and of the 

 purulent exudations generally. Another circumstance which calls 

 for attention is, that to render an analysis of the pus thoroughly 

 useful, it is essential to institute simultaneously an analysis of the 

 blood; yet what physician would be so unconscionable as to 

 prescribe venesection in the case of a patient in whom the 

 purulent discharge was so copious as to afford the chemist sufficient 

 materials for a proper analysis ? We must, therefore, necessarily 

 content ourselves with having recourse to the lower animals for 

 this purpose. There is nothing of chemical pedantry in desiring 

 parallel analyses of the blood, but yet the accuracy of a physico- 

 scientific inquiry would not be invalidated by its omission. It is 

 obvious that the constitution of the pus must in a great degree be 

 dependent on that of the blood, and that an accurate examination 

 of the former must embrace a notice of the character of the blood 

 also; but one would hardly believe that this influence could extend 

 so far as to manifest itself in the physical character of the cor- 

 puscles ; yet it is by no means difficult, after some little practice, 

 to determine from the form, size, granulation, &c., of the cor- 

 puscles, the nature of the source from which they have originated. 



