USES OF PUS. 193 



acute pneumonitis, containing casts of the tubes and cells filled with 

 oil-globules, is shown by Fig. 108. 



Finally, pus cannot be absorbed from a part without disintegra- 

 tion of the corpuscles, and then reappear in another part, as some 

 still maintain. It may enter the blood through openings in the 

 vessels (as in stumps, &c.), but in no other way. 1 



Uses of Pus. 



1. Pus, being a bland fluid, is incidentally useful when formed upon 

 granulating surfaces, in protecting the subjacent layer of the exuda- 

 tion from the action of the air, and thus enabling it to be organized 

 into tissue instead of pus. The granulations themselves also would 

 be reabsorbed, and the reparative process arrested, if the air were 

 not thus kept from them. It follows, therefore, that whenever it is 

 impossible to exclude the air from a granulating surface by artificial 

 means, the pus should not be entirely removed when the dressings 

 are renewed ; but only any excess, or any portion which has under- 

 gone or may soon undergo decomposition. Here, then, pus is inci- 

 dentally useful ; though its formation i. e. suppuration is not de- 

 sirable, were it possible to secure the organization of the whole of 

 the exudation into new tissue. 



2. Again, when an exudation has become coagulated in a part, or 

 on a mucous membrane, it is sometimes better that it should be 

 organized into pus than into tissue, provided it cannot be reab- 

 sorbed ; for then it may be removed from the part. E. g. in pneu- 

 monitis the exudation had better become developed into pus-cor- 

 puscles and fatty molecules (gray hepatization), and be removed in 

 the sputa, than become organized into an indurated mass, destroying 

 the pulmonary structure. And if the exudation in true croup is 

 converted principally into pus and removed by the act of coughing, 

 instead of taking the form of a tough false membrane, so much the 

 better for the patient. In such cases, therefore, the formation of pus 

 is an advantage; in other terms, suppuration is an advantage, though 

 the pus itself is of no use in the organism. 



3. On the other hand, suppuration is always directly destructive of 

 the exuded plasma i. e. it prevents the latter from being organized 

 into tissue. Hence profuse suppuration produces a powerful exhaust- 

 ing effect upon the organism, unless neutralized by an abundance of 

 nutritious food. The emaciation which it also produces is easily ex- 

 plained by the abundance of fat in pus, there being, on an average, 

 at least ten to fifteen times as much, proportionally, as in the blood. 

 Hence the use of cod-liver oil seems to be indicated here as well as 

 in scrofula and phthisis. It also follows that in all cases of repair 



1 Vogel mentions a case of empyema in which a thick creamy fluid escaped in 

 the urine when the thoracic effusion subsided. The microscope, however, showed 

 that the urinary admixture consisted entirely of epithelial debris. 



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