| P. ringeri. | P. westermanii. | P. kellicotti. | |
| Shape | Chisel-shaped, mod- erately heavy. | Lancet-shaped, very slender. | Chisel-shaped, heavy. |
| Distribution | Circular rows, in groups. | Circular rows, in groups. | Circular rows, singly. |
Two other species, P. rudis, Diesing, 1850, in a Brazilian otter (Lutra brasiliensis) and P. compactus, Cobbold, 1859, in the Indian ichneumon, are but little known.
Habitat.—Lungs, pleuræ, and especially the bronchi of man and dog. The alleged occurrence (of eggs) in other organs may be due to confusion with those of Schistosoma japonicum.
Fig. 151.—Egg of Paragonimus ringeri, Cobb., from the sputum. Showing the ovarian cell and vitelline cells and granules. 1,000/1. (After Katsurada.)
Distribution.—China, Korea, and especially in Japan, where, according to Katsurada, there are no districts that are entirely free from pulmonary flukes. The mountainous provinces of Okayama, Kumamoto, Nagano and Tokushima are the principal centres.
Pathology.—The number present in the lung varies from two to twenty, about. Usually one cyst contains one worm, but in the dog each cyst contains two. The cysts admit the tip of the finger, and have a fibrous wall 1 mm. thick. They originate partly from dilatation of bronchi and bronchioles. Others arise from the inflammatory reaction of lung tissue into which the worms have wandered. The worms and their eggs cause bronchitis and peribronchitis, catarrhal, hæmorrhagic, or purulent, and areas of consolidation. Areas containing eggs in their centre resembling tubercle nodules are not uncommon, and extensive cirrhosis of the lung may be found. As a result of these changes, emphysema and bronchiectasis also occur.
As to the development, only the following details are known: that the eggs, which before segmentation of the ovum reach the open in the sputum and through being swallowed also in the fæces, develop in water into a miracidium ciliated all over, which hatches and swims about freely. According to Manson this takes place in four to six weeks.