HYDATID TUMOURS OF THE LIVER. 701 



cyst of semitransj^arent elastic material of very variable size 

 and form, within which, floating in a limpid colourless fluid, 

 are numberless minute organisms, immature forms of the Taenia 

 ecchinococcus. In size these hydatid tumours vary from the 

 bulk of a hazel-nut to that of an orange, or even larger, while 

 their form is regulated according as they are maternal brood- 

 cysts, secondary, or tertiary productions ; they appear to de- 

 velop by a multilocular process, both endogenously and exo- 

 genously. Even when encroaching considerably upon the 

 structure of the liver, which they seem to do chiefly in virtue 

 of their physical bulk, they do not appear to give rise to appre- 

 ciable disturbance, and rarely is their presence even suspected 

 during hfe. 



That in certain conditions they might prove dangerous is 

 easy to be understood ; that they rarely do so is tolerably well 

 established ; while we are aware that many of them become 

 abortive, and are found on death filled with a pasty sabulous- 

 looking material, which may have caused the death of the 

 organisms, or have resulted from their arrested vitality. 



V. Other Changes and Accumulations of Morbid 

 Products in the Liver. 



In addition to these retrogressive and destructive changes 

 noticed we occasionally encounter others which are only pro- 

 bably less important and less serious because less commonly 

 occurring. Pigmentary changes, cancerous and lymjphoid 

 growths, are to us exceedingly interesting, if only as post- 

 mortem curiosities. The usual form which cancer assumes in 

 the liver of the horse is that of nodules or irregular masses, in 

 consistence between scirrhus and encephaloid; while on appear- 

 ing on the surface of the organ these growths are disposed to 

 flatten and spread out. The liver itself in such invasions is 

 considerably enlarged and somewhat altered in shape. In 

 conjunction with these growths there is often evidence that 

 accompanying them at some stage of their development, pro- 

 bably on appearing at the surface of the organ, more or less 

 inflammatory action has existed, affecting the covering of the 

 organ and contiguous textures. 



In growth and stability these mahgnant products exhibit 

 great varieties; the softer being disposed to increase with 



