622 DISEASES OF THE HOBSE. 



wise by intravenous or subcutaneous injections of blood and of 

 emulsions made from nasal discharge, urine, the lung, and other 

 organs. 



The most recent experimental results of Gaffky and Liiher proved 

 that at least at the beginning of the disease the bronchial secretion 

 contains the infection. Upon killing horses affected with the typical 

 forms of the disease on the third or fourth day of the affection the 

 air passages are usually found to be filled with a yellowish, tena- 

 cious, germ-free secretion with which they succeeded in infecting 

 healthy colts The virus has not been isolated. The possibility of 

 its being a protozoan is suggested by the above-named investigators 

 through their observations of round or rod-shaped bodies in the 

 round cells of the secretions. 



Two organisms were formerly especially considered to play an im- 

 portant part in the cause of the disease, the Streftococovs 'pyogenes 

 eqm, which has been isolated from most cases of the disease, and the 

 Bacillus eqmsepHous, which by some investigators was considered to 

 be the cause of contagious pleuropenumonia. Although there is 

 no doubt as to the presence of these microorganisms in most of the 

 cases, their association with the cause of this disease, however, is 

 now doubted, especially since attempts to transmit the disease with 

 pure cultures of these germs failed to reproduce the typical form 

 of the disease. They, however, are of great significance in connection 

 with the pathological changes occurring in connection with the infec- 

 tion and probably are the determining factor in the course of the 

 disease. They exert their action after the animal has already been 

 attacked by the true virus, and then produce the inflanmiatory 

 changes attributed to these secondary invaders. 



This disease is the adynamic pneumonia of the older veterinarians, 

 who did not recognize any essential difference in its nature from 

 an ordinary inflammation of the lungs, except in the profound seda- 

 tion of the force of the animal affected with it, which is a promi- 

 nent symptom from the outset of the disease. Again, this same 

 prostration of the vital force of the animal, combined with the 

 staggering movement and want of coordination of the muscles, 

 caused it for a long time to be confounded with influenza, with which 

 at certain periods it certainly has a strong analogy of symptoms, 

 but from which, as from sporadic pneumonia, it can be separated 

 very readily if the case can be followed throughout its whole course. 



Infectious pneumonia is a specific inflammation of the lungs, ac- 

 companied with interstitial edema and inflammation of the tissues of 

 these organs and a constitutional disturbance and fever. It causes 

 a profound sedation of the nervous system, which may be so great as 

 to cause death. It is sometimes attended with pleurisy, inflamma- 

 tion of the heart or septic complications, which also prove fatal. 



