METASTRONGYLIN^ 263 



The worms may be in masses sufficient to obstruct the medium-sized 

 or larger bronchi which in places may present sac-like dilations con- 

 taining bundles of worms together with more or less purulent mucus. 

 The mucosa of the heavily infested bronchi is edematous and may show 

 hemorrhagic streaks. In the vicinity of bronchial dilations especially 

 there is proliferation of connective tissue, the air-containing tissue 

 being compressed and obHterated and at the periphery sometimes 

 showing locahzed pleuritic adhesions. 



In pneumonia due to the presence of strongyles three forms have 

 been distinguished, viz: 1. A lobar pneumonia due to the presence of 

 the adult worms in the ramifications of the bronchi. 2. A diffuse pneu- 

 monia due to ova and embryos which invade the pulmonary tissue in 

 large nimibers. 3. A nodular or pseudo-tuberculous pneumonia due 

 to the accumulation of eggs and embryos in circumscribed parts of the 

 lungs. The last is the most common form and is characterized by the 

 presence of small, hard, grayish yellow centers from the size of a millet 

 seed to that of a pea which may be more or less confluent. Most of 

 these nodules are found toward the periphery of the lungs, particularly 

 at the margins and just beneath the pleura. Generally they adhere 

 closely to the surrounding tissue, varying in color from j'ellow, grayish 

 yellow, reddish brown, violet, or black according to their age and the 

 character of the inflammatory process. All of the centers become caseous 

 and finally undergo calcareous infiltration. 



In addition to the bronchial and pulmonary lesions there are presented 

 in severe cases the evidences characteristic of anaemia and cachexia, 

 involving subcutaneous edema and serous exudate in the cavities of the 

 body. 



Dogs which have suffered from cardio-pulmonary strongylosis will, 

 on necropsy, reveal adult worms {Hosmostrongylus vasorum) in the right 

 heart and branches of the pulmonary artery. The lungs at the bases of 

 their lobes show circumscribed granular areas in which the tissue is 

 gray, compact, and heavier than water. The granules are hardly the 

 si-ze of a pin's head, semi-transparent, and give a roughened aspect to 

 the surface. About the eggs and embryos lodged in the small arterioles 

 there are found small pseudo-foUicles which, on histological examina- 

 tion, will exhibit three zones, — (1) a central consisting of a giant cell 

 containing a segmented egg or embryo; (2) a middle of epithelial cells; 

 and (3) a peripheral consisting of embryonal tissue elements disposed 

 circularly. Larger nodules may be found, usually in close relationship 

 to a clot in a branch of the pulmonary artery in the vicinity of which 

 there is an accumulation of adult strongyles. 



Development and Etiology. — The lungworms deposit their eggs in 

 the respiratory passages of their host and the freed embryos are either 

 expelled directly with the bronchial secretion or, passing to the pharynx, 



