Anatomical Changes. Synii^tonis. 47 



laryngitis due to an infection. Catching cold appears to play 

 a predisposing role, because most of these cases are seen in 

 spring and fall, on damp days or after sudden changes of 

 temperature, also after a sojourn in the open during cold nights 

 (according to Forneris often seen in the mountains oi Piedmont). 

 The microbe causing this infection is not as yet definitely known. 

 Some observations, however, of Ernst seem to point to the 

 bacillus necrophorus as the etiologic factor. This bacillus is 

 frequently present upon the mucosae of herbivora and it mav 

 do harm if the resistance of a mucosa is lessened or if the bac- 

 terium has attained a higher degree of virulence. Other bac- 

 teria, perhaps streptococci, may have a similar effect. 



The disease sometimes occurs secondarily in infectious 

 diseases with similar or diphtheritic inflammations of the 

 neighboring organs. Such diseases are: malignant catarrhal 

 fever and croup of cattle, diphtheria of fowls and calves, 

 rinderpest, sheep-pox, purpura hemorrhagica of horses, acute 

 glanders, etc. 



Anatomical Changes. Elongated, cylindrical or tubular 

 fibrinous pseudomembranes are found at the base of the 

 epiglottis, at the epiglottic-arythenoid bands, and also at the 

 other portions of the larynx, and not uncommonly farther down 

 an the trachea and even in the first portions of the bronchi. 

 The membranes are 1-3 mm. thick in smaller animals ; in larger 

 animals considerably thicker grayish-white, or brownish in 

 color. They are sometimes quite loose, almost liquid; at 

 other times firmer and dryer. They are freq^uently partly 

 detached, especially at the periphery, and still adherent in other 

 portions. Under the pseudomembranes the mucosa is intensely 

 reddened, sometimes containing extravasated blood, and in the 

 deeper layers infiltrated serously or purulently. Sometimes 

 the inflammation shows a diphtheritic character and deep losses 

 of substance are then seen after the removal of the pseudo- 

 membranes. 



The substance of the pseudomembranes presents an amorphous or reticular 

 mass which contains white and some red blood corpuscles, also here and there 

 epithelial cells in lumps, and various bacteria in the more superficial strata. The 

 membranes swell up under the influence of acetio acid or ammonia, while they are 

 dissolved by the caustic alkalies, lime water or lactic acid. 



Post-mortem examination also shows other changes, namely, 

 purulent bronchitis, catarrhal or croupous pneumonia, atelec- 

 tasis of the lungs, acute swelling of the cervical and intra- 

 thoracic lymph glands in cattle, also frequently croupous 

 gastritis and enteritis. There are also usually signs of death 

 from suffocation. 



Symptoms. Croupous inflammation of the larynx begins 

 with the symptoms of an acute laryngitis which increases 



