. Diseases of cattle, sheep, goats and swine. Veterinary medicine. 294 DISEASES OF THE LIVER. the biliary ducts of oxen, sheep, and goats of two species of distomata, viz., the Distoma Iwpaticum or Fasciola Iwpatica, and the Distoma lanceo- latam. In 1875 Zundel established the causative relation between the pre- sence of distomata in the liver and the development of progressive fatal cachexia in most of the animals affected. This B opinion was emphasised by the works of Leuckart and Thomas on the development of distomata, and at the present day the parasitic theory is accepted as beyond quest
. Diseases of cattle, sheep, goats and swine. Veterinary medicine. 294 DISEASES OF THE LIVER. the biliary ducts of oxen, sheep, and goats of two species of distomata, viz., the Distoma Iwpaticum or Fasciola Iwpatica, and the Distoma lanceo- latam. In 1875 Zundel established the causative relation between the pre- sence of distomata in the liver and the development of progressive fatal cachexia in most of the animals affected. This B opinion was emphasised by the works of Leuckart and Thomas on the development of distomata, and at the present day the parasitic theory is accepted as beyond question. Fasciola hepatica {Distoma hcpaticnin).—The connnon liver fluke of cattle, sheep, swine, etc. Life history. The adult parasite, instead of producing young similar to itself and capable of developing directly into adults in cattle, pro- duces eggs which develop into organisms totally different from the adult form, living a parasitic life in other animals. In scientific language, the parasite is subject to an alternation of genera- tions, together with a change of hosts. The fol- lowing summary of the life history will make this point clear:— («) The adult Itennaphroditic worm (Figs. 144 and 145) fertilises itself (although a cross fertilisation of two individuals is not impossible) in the biliary passages of the liver, and produces a large number of eggs. {b} Eggs (Figs. 143, 146 and 147).—Each egg is composed of the Fig. 142.—Fr^s•r(•o/r iica. A, yoiin: adult parasite. Railliet.). Fig. 148.—Eggs of Fasciola Itc^'afica. A, from the bile duct; B, embryonic ; C, after opening. (After Eailliet.) Fig. 144.—Common liver fluke {Fasciola hejxi- tica), natural size. (Stiles, Annual Report, Bureau of Agri- culture, 1901.) following parts : (1) A true germ cell, which originates in the ovary and is destined to give rise to the future embryo; (2) a numl)er of vitelline or yolk cells, which are formed in a specialised and independent portion (vitellogene gland)
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectveterin, bookyear1920
