108 DISEASES OF POULTRY. 



place chiefly in the mucous membrane or the sub -mu- 

 cous tissue, or it may, though rarely, extend into the 

 muscular coat. According: to Smith, the parasites do 

 not invade the epitlielium at any time. 



The changes in the liver are most easily exi)lained 

 by assuming that the micro -parasites are conveyed by 

 the Ijlood directly from the diseased cx^ca into the liver 

 and there deposited in different places. In this organ, 

 they begin to multiply and spread in all directions, 

 thereby forming the spherical centers of disease which 

 appear as circles on the surface of the liver. This 

 theory is borne out by the results of the microscopic 

 examination. 



The course of the disease is variable. In some cases, 

 it develops rapidly after infection and the affected 

 birds die in from two to six weeks. In other cases, 

 the morbid process may come to a standstill, but the 

 amount of dead tissue in the cceca and 

 liver may be so great as to favor the 

 entrance of bacteria, which are directly 

 responsible for the death of the bird 

 late in the summer or fall. In still 

 other cases, regenerative processes may pitr. :i.-The rro- 



, . liji It 3„ ^_ tozoa as lliev apoear 



begni and lead to complete and perma- when separated fn.m 



fresh tissue, x 1000. 



nent recovery. 



During the course of the affection, the parasitic pro- 

 tozoa multiply in the caeca, they are mixed with the 

 intestinal contents, and many of them are discharged 

 with the excrement. In this way the contagion is 

 spread. The food and drinking water become con- 

 taminated with particles of excrement containing the 

 parasites, the latter are taken by healthy birds into the 

 digestive canal along which they proceed until the 

 cceca are reached, and here they multiply, penetrate 



