83 



As the animals were submitted to 

 closti observation only some time after 

 the work was begmi, I was obliged to 

 separate the animals into groups of very 

 different demonstrative value. 



Thus we have a Group I, in which 

 the rabbits had a normal number of 

 leucocytes during the term of obser- 

 vation and were killed without having 

 suffered inoculation; Group II, the most 

 important, comprehending animals under 

 the same conditions as in Group I, 

 but having been killed or having died 

 in different stages of immunisation. 



A Group III consists of animals that 

 showed an abnormal number of white 

 blood corpuscles during the term of 

 observation. 



In a Group IV, finally, I included all 

 the rabbits that where not observed 8 

 days before being used for experimenta- 

 tion. 



In this way each group serves as m. 

 control for the others, and constitutes 

 a valuable material for comparative 

 study. 



This is a highly important point 

 in the case of animals very sensitive 

 to bad conditions of housing and fee- 

 ding and liable to suffer from various 

 diseases, the more so in the case of m 

 study on a tissue like bone-marrow that 

 shows important alterations in animale 

 which at first sight appear perfectly 

 normal. 



