JO Aug.. igr^.] The h'jiologv of Conta^^mus Diseases. 



495 



I'lG. 14. BLACK LEGHORN HEN SUFFERING FROM ACUTE SPIROCH AETOSIS. 



the form of a spirillum (l^'ig. 15). 

 and is transferred from bird to bird 

 by means of the tick ; it is from 

 I /600th to I / I, 600th of an inch 

 long. The difficulty in eradicatinjj; 

 these diseases is apparent, for so 

 long as the tick remains in a dis- 

 trict, it is capable of continuing 

 the spread ; and as som.e of the 

 t'cks are capable of long life, even 

 without food, the tlifficulties are 

 increased. The tick concerned in 

 the spread of the disease in poultry 

 is capable of living for a period 

 •of three years or more without 

 food. 



A variety of parasite, which, 

 fortunately, is not present in Aus- 

 tralia producing any pathogenic 



FOWL SPIROCHAETOSIS. FREE 



SPIROCHAETES AND TANGLES 

 THE ACUTE STAGE. 



DURING 



TIG. 16. TRVPANOSOMES OF I AND 



5 



SURRA, 3 .AND 4 NAGANA, 

 AND 6 MAL DE CADERAS. 



effect, is the 

 Trvpanosoina 

 (Fig. 1 6). These 

 organisms live 

 in the blood ot 

 various hosts 

 and cause a 

 \' a r i e t \' o t 

 s )' ni p t o m s . 

 Some of the 

 diseases pro- 

 duced may be 

 familiar by 

 name, as ex- 

 ample," Surra" 



