Abstract
Muellerius capillaris was first described by Mueller in 1889 who placed it in the genus Pseudalius; it was transferred in 1907 by Railliet and Henry to their new genus Synthetocaulus. In 1927, Cameron, in his review of the family Protostrongylidæ Leiper, 1926, created the genus Muellerius to include this species; a description of this parasite together with figures of the adult and the larval stage commonly met with in the lungs and droppings of sheep and goats, is included in his paper.M. capillaris inhabits the bronchioles and alveoli of the lungs of sheep and goats but is probably more often observed in the connective tissue of the lungs where it forms nodules of varying sizes. In heavy infestations these nodules are so close together that they appear as large greyish patches on the surface of the lung. The nodules eventually become calcified.