MUSCULAR CHANGES. 529 



The perimysium sends off connective-tissue fibers which pass 

 between the individual muscle fibers. These constitute the en- 

 domysium. Plates II (d) and III (d) show the endomysium 

 around the individual muscle fibers. In places the endomysium 

 is infiltrated with a slight fibrinous exudate intermingled with 

 leucocytes, while in other places it has become hyperplastic by 

 the new formation of connective tissue. Now and then new- 

 forming blood vessels are found in this hyperplastic endomy- 

 sium, Plate III (b), showing the presence of a productive 

 inflammation. 



It will be noticed that the muscle tissue situated closest to the 

 epimysium has undergone the most marked pathological changes. 

 Plates II (e and /) and III (c and e) . This seems plausible as the 

 predominant changes are situated in the epimysium, the exudate 

 of which by continuity extends among the muscle fibers. In 

 these areas the endomysium is distended with a fibrinous exudate 

 which is composed of large numbers of leucocytes, especially in 

 the vicinity of the bands of cells mentioned above. Under the 

 influence of this exudate, the muscle fibers become in some 

 instances filled with vacuoles, lose their striations, take on a 

 granular appearance, and lose their nuclei. Thus they present a 

 typical picture of granular degeneration which may be brought 

 about by the coagulation of the exudate around them, shutting 

 off their nutrition, or the toxin from the pleuropneumonia virus 

 may have a vital influence- 



Another characteristic lesion is the degeneration atrophy of 

 the muscle fibers. In many cases the fibers have completely 

 disappeared, leaving the endomysium surrounding the spaces 

 which were once occupied by them. 



Upon examination of sections of tissue thus affected, muscle 

 fibers are found in all stages of degeneration, and as the degenera- 

 tion advances the fibers become more shrunken and finally 

 disappear entirely. 



CONCLUSIONS. 



1. From all appearances, the contagious pleuropneumonia virus 

 seems to have a specific action upon muscle and connective tissue, 

 affecting chiefly the connective-tissue elements. 



2. The appearances suggest that the virus multiplies in the 

 lymph spaces of the connective tissue and blood vessels, gradually 

 working its way through the walls of the blood vessels, causing 

 an inflammation of the intima and thus giving rise to thrombus 

 formations. 



