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formsa very minute tubercle. When this tubercle has rea(;he(l fronioueto 

 two and one-halt in illiuieters (onotweuty-liftli to one-teutli of an inch) iu 

 size, it is composed of a distinct central part, tilled with a soft, greenish, 

 central portion, which is surrounded by a thicker membranous capsular 

 portion, composed of cells of new growth, the inner part of which degen- 

 erates later and enters into the formation of the cheesy central mass. 

 Within this tubercle is the young parasite. In later stages this tubercle 

 enlarges until it becomes 3'""' in diameter. In this stage the soft interior 

 mass will be firmer. The parasite is always found between the interior 

 mass and the capsule, and is surrounded by the soft, freshly- formed 

 greenish material, which it seems to produce by the irritation of the 

 adjacent capsule. When the parasite attains its adult size it evidently 

 breaks from the tubercle and thereafter lives in the adjacent bronchioles. 

 There is quite a diiference in the external appearance of the little tuber- 

 cles during the different stages of growth. In the earlier stages they 

 appear as little blood-red spots just beneath the pleural coat of the 

 lung ; later they look like little brownish fluid-filled tumors, surrounded 

 by a red zone; still later a yellowish, green, cheesy material appears in 

 their center, and the tumors present a greenish-gray appearance. The 

 gray is due to the thickened capsule and a thickening of the pleural 

 coat of the lung over the little tubercle. There is usually a slight ele- 

 vation of the surface of the lung over these nodules, but this feature is 

 dependent on the depth at which the nodule is situated. They may 

 occur at any depth in the lung substance, but are usually near the sur- 

 face. When the parasite escapes from the nodule a new phase of the 

 disease begins. It wanders through the bronchi until it meets one of 

 the opposite sex, when they mate. Soon after the female begins to lay 

 eggs in the bronchioles and alveoli, which she infests, and these eggs 

 in turn hatch into young worms. These young worms are very lively, 

 and help to increase the disturbance of vital functions of the lung sur- 

 rounding them. That part of the lung then becomes as if sodden, the 

 air tubes fill with eggs, worms, cast-off epithelial cells, mucus, wan- 

 dering cells, and air globules ; the tissues of the walls of the alveoli 

 become thickened and encroach upon the contents, and the function of 

 the part. is entirely suspended. The effect of the worm and its brood 

 at this stage is to produce a pneumonia, hence the disease has been 

 termed verminoun pneumonia. This pneumonia is limited to the neigh- 

 borhood of the parasite and does not extend beyond. The patches are 

 from 1 to 2.5^'" in width, but in those recently formed they rarely ex- 

 tend more than 2 or 3""" deep. The injury seems to be mainly a me- 

 chanical effect, due to the irritation set up by the parasites. When 

 one of these patches is cut into a frothy liquid exudes, bearing quanti- 

 ties of eggs and embryos in all stages of development. They may be 

 seen with a glass magnifying six diameters. 



In later stages of the disease the tubercles become little hard masses. 

 These have been said to be calcareous, but they are not soluble in acid, 



