COMMON DISEASES AND TREATMENT 169 



resist this disease or other diseases. As a general means 

 of preventing this trouble, care should be taken to see that 

 purchased eggs used for hatching are from flocks that are 

 free from it. 



It has been found that chicks which have white diarrhea 

 but which have recovered from its effects become carriers 

 of this disease. On reaching maturity the disease becomes 

 centrahzed in the ovary or egg-producing organs and thus 

 the disease is transmitted by the hen through the egg to 

 the chick hatched from the egg. When it is apparent that 

 the disease is present in the flock of hens, it can be eliminated 

 by what is known as the agglutination test. This method 

 has been perfected by the Connecticut Agricultural Experi- 

 ment Station. The manner of carrying on this test is as 

 follows: *A blood sample is taken from the hen and a 

 numbered band placed on the bird, a corresponding number 

 being placed on the sample. A bacteriological test is then 

 made of this blood sample by a bacteriologist in an 

 effort to find out whether the hen is a carrier of this dis- 

 ease or not. Many agricultural colleges are now in a 

 position to carry on such tests. "The test is practically 

 accurate, though in some cases depending on the stage to 

 which the disease has advanced, the test may not locate an 

 infected bird, but if the test is carried on through several 

 generations the disease can be eliminated." "The birds to 

 be tested should have laid practically a year before the test- 

 ing takes place; for, if tested sooner than this, they may 

 not react to the test, because the disease will not have pro- 

 gressed suSiciently. Those birds which show that they are 

 carriers of the disease should be eliminated from the breed- 

 ing pen and eggs for hatching should be saved only from 

 those which do not react to this test." 



Trecdmeni. Chickens that have reached the advanced 



* New Hampshire College Extension Circular 44 by A. W. Richardson. 



