8o4' MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



constant, but a pericarditis is usually seen. There may be, also, con- 

 gestion of the lungs, liver, and kidneys. The intestinal lesions are not 

 as marked as is the case in chicken cholera. 



Chicken pest has been shown to be due to an invisible microorgan- 

 ism which is present in the heart blood and in practically all of the 

 organs of the body. Most fowls are susceptible; guinea-pigs and mice 

 are refractory to the disease. The virus passes through Berkefeld 

 and Chamberland F cylinders; it is quite resistant to drying but is 

 destroyed by an exposure of half an hour to a temperature of 60". 

 Several authorities have passed the filtered virus through four or more 

 hens successively, thus demonstrating positively that the filtered virus 

 is capable of multiplication. 



Contagious Bovine Pleuro-pneumonia* 



This disease affects cattle only; it is highly infectious and produces 

 an inflammation of the luUgs and pleural membranes. Thirty years 

 ago bovine pleuro-pneumonia was quite prevalent in the tJnited States 

 but has since been eradicated through the efforts of the Federal Bureau 

 of Animal Industry in cooperation with State authorities. It still 

 exists in European countries. 



The microorganism of bovine pleuro-pneumonia is generally classed 

 among the invisible viruses, though unhke the other organisms of this 

 class it has been cultivated artificially and is just visible at a magni- 

 fication of 2,000 diameters. The artificial cultivation of this virus was 

 accomplished by Roux and Nocard through the use of the very in- 

 genious "collodioif sac method." A small amount of virus from a 

 diseased cow was placed within a small thin- walled sac of collodion; 

 after being hermetically sealed the sac was placed in the peritoneal 

 cavity of a rabbit where it remained for several weeks. At the end of 

 this time the unbroken sac was removed and the previously clear fluid 

 within was found to be slightly opalescent. Microscopic examination 

 revealed numberless minute motile bodies so small, however, that their 

 exact form could not be determined. Later the organism was suc- 

 cessfully cultivated outside of the animal body in a specially prepared 

 bouillon. These cultures produced the disease when inoculated into 

 susceptible cattle. When the virus is diluted it will pass through the 



* Prepared by M. Dorset. 



