The Rot in Sheep. 



33 



produced a quick destruction of the integrity of the liver, with 

 its several concomitants. It is a singular fact, but one which 

 fully accords with our present knowledge of the natural history 

 of the entozoon, that not a single fully matured or parent fluke 

 was met with in these cases. Having preserved several of these 

 entozoa, we here insert a sketch of a group of three of them of 

 their natural size, as drawn to a scale. 



Fig. 1. Young Distomata. 



Vogel has spoken of the young distomata as being four lines 

 long, and one and a half broad. The smallest of our illustrated 

 specimens, however, as will be seen, had not attained even these 

 dimensions ; and, since these were sketched, we have met with 

 many young flukes which were even of smaller size. 



Notwithstanding their minuteness, a microscopical examina- 

 tion showed that the nutritive system of the young distomata 

 — aquiferous and bile-digestive — was fairly developed and in 

 active operation, but that only an outline of the generative 

 organs — the female portion in particular — existed. 



Before leaving this division of our subject we may add a word 

 with reference to the ordinary pathological changes which the 

 liver undergoes from the presence of flukes. When the entozoa 

 are numerous, and especially if the sheep continue to be chiefly 

 supplied with watery food, the liver soon becomes affected with 

 venous congestion, accompanied with a soft or pulpy condition, 

 and an alteration of its natural colour ; otherwise but little 

 structural change takes place until the flukes have attained a 

 medium size, and have travelled onwards from the main biliary 

 duct, which they entered from the duodenum, into its numerous 

 and smaller ramifications for ultimately depositing their ova. 

 Their existence here produces pressure, persistent irritation, 

 and increased vascular action, which lead to the coats of the 

 ducts becoming thickened, and their calibre increased. In 

 medical language, hypertrophy, with dilatation, takes place. It 

 is these changes which give an altered form, and often an 

 increased size, to some parts of the gland. Nature may be said 

 to strengthen the walls of the ducts, even to their minutest 

 divisions, to prevent the entozoa from gaining access to the 

 parenchymatous structure of the liver ; and in effecting this she 

 does not even stop at mere membranous development, but often 

 deposits calcareous materials within the animal tissue 4 . This 

 gives to the liver its hardened condition, and Likewise (mparts 

 a gritty sound on cutting through its substance. The same 



i) 



