MICROBIAL DISEASES OF MAN AND ANIMALS. 651 



and the comb darker in color. The lesions found at autopsy are not 

 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 microorganism 

 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 demonstrat- 

 ing 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 lungs and pleural membranes. Thirty years ago 

 bovine pleuro-pneumonia was quite prevalent in the United 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 unlike the other organisms of this 

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

 of 2000 diameters. The artificial cultivation of this virus was accom- 

 plished by Roux and Nocard through the use of the very ingenious 

 "collodion 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 un- 

 broken 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 successfully 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 Berkefeld and Chamberland F 

 cylinders, but not through the Chamberland B cylinder. 



* Prepared by M. Dorset. 



