Etiology. 199 



in producing the disease processes. The filtrable virus which attacks 

 the body, prepares the field of action for the other organisms which 

 produce inflammatory local changes. Thus Jensen found strepto- 

 cocci, staphylococci and a slender bacillus, Mathis isolated a diplo- 

 coccus from pustules on the skin, the cultures of which resembled the 

 ordinary staphylococcus, Schantyr obtained a motile bacillus resembling 

 the organism of abdominal typhus, Perez incriminated the eocco-bacillus 

 ozoenae foetidus, while Galli-Vallerio found a bacillus resembling 

 the colon bacillus, which, however, stains by Gram. Lignieres, Ceraraicola 

 and "Wunschheim attributed the disease to an ovoid bacterium, and Pior- 

 kowski obtained a slender, delicate capsulated bacillus, etc. 



All of these organisms appear to be normal inhabitants of the 

 dog organism. In different cases one or the other, or several of these 

 organisms commence to multiply more rapidly in the affected dog, 

 and then exert their pathogenic action. This applies especially to 

 the bacillus bipolaris septicus, which was considered by Lignieres as 

 the true cause of the disease. Cultures of this organism (they can 

 only exceptionally be isolated) produce severe septic symptoms in dogs 

 after intravenous injections, and frequently also secondary inflamma- 

 tions in various organs. Whether there exists an independent pas- 

 teurellosis of dogs, as claimed by Lignieres, in addition to the distem- 

 per caused by the filtrable virus, is not established at the present time. 



Contrary to the described etiological findings, Kregenow succeeded in producing 

 the disease with filtrable virus in only two instances out of 10 inoculations, and 

 even the two positive cases he attributes to natural infection. Accordingly he is 

 of the opinion that the virus is not filtrable, and must be one of the numerous 

 visible organisms. However, the experiments, as indicated by his notes, were not 

 carried out as suggested by Carre, with the serous nasal discharge, but with a puru- 

 lent discharge and material obtained from pneumonic lungs. It is possible, therefore, 

 that the filtrable virus contained therein was retained during filtration. 



Natural infection occurs through direct or indirect contact 

 with affected animals. The virus is present in the catarrhal 

 secretion of the mucous membranes and is evidently in most 

 instances taken into the digestive canal with the food and water. 

 The infection is probably favored by influences which reduce 

 the resistance of the body, such as colds, insufficient or im- 

 proper food, such as bread, kitchen refuse, etc. The disturb- 

 ances of digestion caused by these, together with loss of blood, 

 exhaustion, weak constitution, etc., favor the development of 

 the disease. 



Young animals are most susceptible. They may excep- 

 tionally become affected when only 2 to 3 weeks old (Fried- 

 berger & Frohner), but usually dogs several months old up to 

 one year suffer most frequently from the disease (this is prob- 

 ably due to the fact that the animals at that age move around 

 more freely and are more exposed to the infection). The 

 susceptibility diminishes with advancing age, so that animals 

 over three years old are but rarely affected. The great re- 

 sistance of older animals is in all probability due to the fact 

 that the great majority have been affected with the disease 

 at a younger age and have thereby become immune to it. 



Pampered and weakly dogs, as well as animals recently 



