penetrate into the interior of the separate muscular bundles, and here already, after fourteen days, acquire the size and organisation of the well-known _Trichina spiralis_. (9) Soon after the intrusion of the parasite the infested muscular fibre loses its original structure, the fibrillæ collapse into a finely granular substance, whilst the muscular corpuscles change into oval nucleated cells. (10) The infected muscular bundle retains its original sheathing up to the time of the complete development of the young Trichinæ, but afterwards its sarcolemma thickens, and begins to shrivel at the extremities. (11) The spot inhabited by the rolled-up parasites is converted into a spindle-shaped widening, and within this space, under the thickened sarcolemma, the formation of the well-known lemon-shaped or globular cysts commences by a peripheric hardening and calcification. This degeneration commences several months after the wandering. Immature muscle-Trichinæ are not capable of producing infection. (12) The migration and development of the embryos also take place after the transportation of impregnated Trichinæ into the intestines of a new host. (13) The further development of the muscle-Trichinæ into adult animals is altogether independent of the formation of the calcareous shell, and occurs as soon as the former have reached their completion. (14) Males and females are already recognisable in their larval state. (15) The immigration of the Trichina-brood in masses produces very grave or even fatal consequences, such as peritonitis (from the embryos perforating the intestinal walls), pain, and paralysis (resulting from the destruction of the infected muscular fibres). (16) The infection of man occurs especially through swine. (17) The muscle-Trichinæ are so capable of resistance that they are by no means in all cases destroyed by the ordinary methods of roasting, cooking, pickling and smoking. (18) As a rule, swine obtain Trichinæ from rats, to which latter we also as the natural bearers have to convey them. Microscopic examination of flesh is, therefore, urgently recommended as a public preventive against all danger from Trichinæ.” [Illustration: FIG. 37.--Immature female Trichina from muscle. After Leuckart.]