22 



BULLETIN 817, U. S. DEPT. OF AGRICULTURE. 



when cut but cutting with difficulty, indicating a beginning indura- 

 tion. 



The lesions in the lungs are more striking macroscopically than 

 those in the liver. In our mildest cases there were small bright-red 

 hemorrhagic spots, in which the larvae usually could be discovered 

 without difficulty. As a rule the lungs were more or less edematous. 

 The small bright-red petechial hemorrhages and edema are very 

 characteristic of Ascaris invasion and differentiate it from other 

 conditions that are likely to be seen in the lungs of pigs. In mor§ 



Fig. 5. — Ascaris sunm. Larva in section of lung of mouse 1 week after infection. 

 Photomicrograpli. Highly magnified. 



severe cases there were ecchymotic patches of considerable size, giv- 

 ing the lung a spotted appearance. In still more severe cases an 

 entire lobe of the lung was involved, and in the worst cases both 

 lungs were greatly swollen, edematous, intensely hemorrhagic, the 

 color of liver, and extensively hepatized. Microscopically the path- 

 ological picture varied from that of an acute lobular pneumonia in 

 which the areas of inflammation centered around the bronchioles to 

 lobar pneumonia in the stage of red hepatization. The accompany- 

 ing photomicrograph (figure 6) shows a section of the lung of a 

 mouse with a larva in situ 7 clays after ingestion of Ascaris swurni 

 eggs. In portions of the section will be noted areas of consolidation, 



