14 



SCIENCE. 



[N. S. Vol. XVIII. No. 444. 



cin, tyrosin, xanthin, giianidin, etc. Pus 

 which thus undergoes digestion is capable 

 of dissolving fibrin and even portions of 

 organs independent of the action of bac- 

 teria. Prom this the conclusion can be 

 drawn that pus, or really the leucocytes of 

 pus, possess active digestive properties, a 

 fact which the history of abscess forma- 

 tion and the removal by leucacytes of ne- 

 crotic and other kinds of tissue, renders 

 easily comprehensible. Many years ago 

 Weigert attempted to explain, by assuming 

 the operation of a peculiar poison which 

 prevented fibrin-formation, the absence of 

 fibrin from abscesses, etc., in which the 

 fibrin factors must have originally been 

 present. It is much more probable that 

 what happens is a digestive transformation 

 of fibrinogen, or of fibrin at the moment 

 of its formation, by the ferments of the 

 pus cell. 



Broadly speaking, exudates and necrotic 

 tissue are removed in two ways: (1) by 

 absorption, and (2) by organization. In 

 the first mode disintegration and solution 

 of the cells, etc., with the exception of the 

 fat and certain other elements, such as pig- 

 ment, take place, and an emulsion results 

 well adapted for entrance into the lym- 

 phatics. In the second, new vessels de- 

 velop and invade the exudate or necrotic 

 tissue, and by supplying a fresh set of 

 leucocytes to dispose of the offending ma- 

 terial, it is finally removed. From what 

 has already been said, the first series of 

 changes will readily be recognized as caused 

 by autolysis ; but the operation of the same 

 cause is not so apparent in the second series. 

 And yet, the two series are essentially the 

 same. In the one the original material 

 contains ferments of a kind and a quantity 

 sufficient to bring about the transformation 

 which is necessary before absorption can 

 take place; in the second, the ferments 

 being originally insufficient, are renewed 



by fresh leucocytes which emigrate from 

 the vessels, load themselves with debris, and 

 finally accomplish their entire removal. 



There is little doubt that in many patho- 

 logical conditions the leucocyte is the es- 

 sential agent in bringing about absorption ; 

 and what is required to accomplish this 

 end is not living leucocytes so much as 

 large numbers of these cells, since autolysis 

 proceeds independentl.y of the vitality, as 

 such, of the cells. The fate of pathological 

 formations is dependent in large part on 

 the numbers of leucocj'tes present within 

 them. 



The different behavior of a caseous and 

 croupous pneumonia; the facility with 

 which the one and the difficulty with which 

 the other undergoes resolution is to be 

 ascribed probably in part to the absence 

 in large measure of leueocj^tes from the 

 tuberculous process and their presence in 

 enormous numbers in the acute inflam- 

 matory condition. Other examples illus- 

 trating the importance of leucocytes in 

 promoting autolysis and absorption might 

 be given. 



I have been interested for the past two 

 years in studying autolysis of the exudate 

 in the lung in two inflammatory conditions, 

 namely, acute lobar pneiunonia and unre- 

 solved pneumonia. The pathology of the 

 latter condition, except so far as the organ- 

 ization of the exudate is concerned, is, as 

 you know, involved in the deepest obscu- 

 rity. The study of the histology of the lung 

 in various stages of the process of organiza- 

 tion emphasizes one pathological condition, 

 the import of which appears great in view 

 of our present knowledge of autolysis ; the 

 exudate in unresolved pneumonia is fibrin- 

 ous rather than cellular, and many of the 

 alveoli of the lung are filled with dense 

 hyaline fibrinous masses. All attempts to 

 explain upon ordinarj^ etiological grounds 

 the peculiar changes, or absence of changes, 

 in unresolved pneiunonia, have failed ; and 



