[The third period is the PERIOD OF WASTING. This corresponds with the beginning of January--about three months after the entry of the larvæ. Emaciation now becomes very marked, the skin and mucous membranes blanched, temperature variable and marked by an irregular curve; respiration laboured and quick; appetite regular; abortion frequently occurs in pregnant ewes; pressure on the back causes the animals to fall; local œdemas occur, the most perceptible in the submaxillary space, extending below the larynx and over the cheeks and parotids (called “bourse,” “boule” in France; “watery poke” or “cockered” in England). Death usually occurs at this period, but a fourth stage may occur. [The fourth period is the PERIOD OF MIGRATION OF THE FLUKES. This is a period of convalescence and recovery, generally in May and June.--F. V. T.] Oxen suffer less in general, but even in these animals “stray” hepatic flukes are occasionally found in the lungs, enclosed in thick-walled cysts. _Pathological Anatomy._--The bile-ducts are conspicuous on the surface of the liver. They are thickened and much dilated and in parts saccular, and considerable atrophy of the liver cells accompanies the condition. Histologically there is immense proliferation of the epithelium of the bile-ducts leading to “adenomata.” The LIFE-HISTORY of the liver fluke was discovered by R. Leuckart and P. Thomas. According to these investigators the elongated miracidium (fig. 131, _a_) ciliated all over develops from the eggs a few weeks after the latter (fig. 142) have reached the water, and after it has become free the embryo penetrates and becomes a sporocyst (fig. 131, _b_) in a water-snail (_Limnæus truncatulus_, Müll. = _L. minutus_, Drap.) that is common in fresh water, and can live in the smallest collection of water as well as in fields that have been flooded. The sporocyst first of all produces rediæ, which remain in the same host (and under certain circumstances, _e.g._ in summer, these develop a second generation of rediæ), and these finally form cercariæ (fig. 134). The latter become encysted on blades of grass and are taken up by the respective hosts with their food; this takes place towards the end of summer, while the sheep feeding on the pasture land in the spring spread the eggs of the fluke, and sometimes the fluke itself, by passing them with their fæces. In districts where _Limnæus truncatulus_ is absent, analogous species act as the intermediary hosts, of which one example according to Lutz is _Limnæus oahuensis_ in the Sandwich Islands.