162 G. G. Heslop: 



.adds a further complication to the effective eradication of the 

 disease from any particular State. These " recovered animals " 

 are capable of retaining the infective agent in a latent form for 

 -it least several months, and the unsuspected introduction of such 

 animals into healthy herds often provides the starting points of 

 fresh outbreaks. 



Thus, apart from animals in which the disease can be recog- 

 nised by the clinical symptoms alone, the disease is mainly pro- 

 pagated by "carriers" (so called "recovered" animals), or by 

 .affected animals in which the usual clinical signs of the disease 

 are not apparent. The importance of eliminating such animals 

 as early as possible from herds in which the disease has appeared, 

 and the difficulty of attaining the desired object when one has 

 recourse only to the usual clinical methods of diagnosis, made it 

 essential that some more searching and reliable diagnostic method 

 -should be elaborated, which could be applied to such cases, in 

 -order to detect them. It was mainly with the object of attempt- 

 ing to arrive at such a diagnostic method that this present research 

 work was undertaken. 



I desire to express my grateful appreciation and thanks to Dr. 

 S. S. Cameron, Director of Agriculture, Victoria, and to Mr. 

 W. A. N. Robertson, B.V.Sc, Chief Veterinary Officer, Depart- 

 ment of Agriculture, Victoria, for the opportunity and assist- 

 ance they have granted me to pursue the study of contagious 

 pleuro-pneumonia uninterruptedly for close upon twelve months. 



To the staff of the Live Stock Division, Department of Agri- 

 culture, Victoria, I am indebted for the collection of blood samples 

 from infected and non-infected animals, and for post-mortem 

 records of the animals supplying the various sera tested. 



To Professor H. A. Woodruff, Director of the Veterinary 

 Research Institute, Melbourne University, I desire to express 

 my grateful appreciation and thanks, and acknowledge my in- 

 debtedness for the assistance rendered to me by himself and the 

 staff of the Research Institute, during the course of this research 

 work. The work has been carried out in the laboratories of the 

 Veterinary Research Institute, and the materials of the labora- 

 tories, and the assistance of the staff have been placed freely at 

 my disposal throughout. 



To Dr. L. B. Bull, Deputy Director, South Australian Govern- 

 ment Laboratory of Pathology and Bacteriology, I am indebted 

 for much kind advice and criticism of the earlier work on Ag- 

 glutination and Complement Fixation. , tl . ;.,..;.;,, ■ 



