392 POULTRY BREEDING AND MANAGEMENT 



An explanation of the test is given by Dr. Gage of Massa- 

 chusetts as follows: 1 



' ' The two important biological factors necessary for mak- 

 ing the microscopic agglutination test are (1) a test fluid 

 containing a suspension of the organism causing the dis- 

 ease, and (2) a sample' of blood serum from the individual 

 to be tested, and the test is based on the fact that the blood 

 sera of infected and non-infected birds when mixed with 

 the test fluid react differently. The serum of the former, 

 because of the presence of an agglutinin, a substance formed 

 in the body of the bird because of infection with Bacterium 

 pullorum, is capable of producing, when brought in contact 

 with a suspension of the organism, a clumping together of 

 the bacteria, a phenomenon which blood from non-infected 

 birds does not show." 



PARASITES OF FOWLS 



The poultry-keeper must be able to cope with parasitic 

 enemies or they will put him out of ^ business. If every 

 living thing has its own particular pest, the fowl has its 

 full share, probably more than its share. There are a 

 dozen or two insect pests or parasites that have no other 

 business in life, apparently, than that of making life a 

 burden to the chicken. "We do not know how many. The 

 number of varieties, however, is of no consequence com- 

 pared with the number of individuals of any one variety 

 that may be propagated or born into the world in a few 

 days. From one single louse in the third generation, there 

 may be produced in eight or nine weeks over 100,000 in- 

 dividual lice, each one hatched from an egg. 



The different varieties work in different ways. One 

 variety sucks the blood from the chicken and when, tens 



1 Massachusetts Bulletin No. 163. 



