200 Distemper of Dogs. 



imported, especially those of the finer breeds, are more sus- 

 ceptible and usually become more severely affected than do 

 dogs which are kept in the country and are hardened. 



Pathogenesis. The action of the specific virus produces a 

 febrile condition, and in direct association with it catarrh of 

 the mucous membranes, as well as inflammation of the serous 

 membranes, especially of the pericardium. If the animal lives 

 through the acute attack, its weakened resistance favors the 

 development of secondary processes by other micro-organisms. 

 These are usually facultative pathogenic bacteria, which are 

 mostly, or probably invariably, frequent habitants of the healthy 

 dog. Of the secondary inflammations the most frequent are 

 pneumonia, purulent inflammations of the conjunctivae, the 

 mucous membranes of the air passages and of the intestinal 

 canal, pustules on the skin, and also inflammatory changes 

 in various parts of the nervous system as a result of metastasis. 

 The later course of the disease depends on these secondary 

 diseases, while the filtrable virus usually disappears before, 

 or not later than at the beginning of their development. 



Anatomical Changes. In the rare peracute cases a large 

 quantity of serous fluid is present in the pericardium, and 

 possibly there are small hemorrhages in the heart muscles. 



In the great majority of cases the respiratory organs, es- 

 pecially show severe changes. The mucous membranes of the 

 air passages are bright red, swollen, and profusely covered 

 with sero-purulent secretion. If the smallest bronchi are af- 

 fected simultaneously numerous small purulent plugs may be 

 squeezed out of the cut surface of the lungs (bronchitis 

 capillaris). In most cases there is also a catarrhal pneumonia. 

 Sometimes small broncho-pneumonic areas may be disseminated 

 throughout the lungs, or larger lung portions, especially near 

 the anterior and lower borders are found dense, hepatized, and 

 according to the duration of the inflammation either dark 

 brown-red or grayish-red. The cut surface is smooth or finely 

 granulated, and sometimes studded with small purulent foci. 

 The borders of the unaffected lobes of the lungs show bluish-red, 

 depressed, club-shaped atelectatic areas. The pleura covering 

 the affected parts of the lungs is either smooth and lustrous, 

 or dull and covered with fine fibrinous membranes. 



The mucosa of the stomach and intestines show frequently 

 manifestations of acute catarrh; the solitary follicles, as well 

 as Peyer's patches are swollen. Exceptionally there may also 

 be superficial erosions and catarrhal ulcerations present. 



The lymph glands of the thoracic cavity, and of the 

 mesentery show inflammatory swellings; the pericardium con- 

 tains sometimes a great quantity of a clear serous fluid. The 

 heart muscles may be interspersed with small hemorrhages and 

 yellow fatty degenerated areas. The liver and the cortical 

 portions of the kidneys show parenchymatous or fatty de- 



