Pathogenesis. Anatomical Changes. 335 



The virus which penetrates between the epithelial cells of these 

 parts of the body in all probability commences to multiply im- 

 mediately, later however it passes into the blood stream, by 

 which it is distributed to distant parts, of the body. The affec- 

 tion of feet and udder, which later becomes associated with the 

 affection of the mouth, may be of such metastatic origin. 



_ The virus may be transmitted from the mother to the off- 

 spring, in which case the young may be born showing manifes- 

 tations of foot-and-mouth disease (Mobius). 



According to Kitt the development of the vesicle commences with hyperemia 

 and serous infiltration of the papillae of the skin or mucous membranes. The 

 serous exudate loosens the epithelial cells from the mucous layer between the 

 papillae, then it raises the more resistant, superficial layer of cells, while the contents 

 of the developed vesicles in the meantime becomes cloudy, as a result of migration 

 of white blood corpuscles. The epithelial defect which develops after the bursting 

 of the vesicles becomes covered by epithelial cells which form either from the 

 remaining part of the stratum mucosum, or by a multiplication from the periphery, 

 and complete healing takes place in this manner, except that the papillae become 

 somewhat smaller than they were originally. 



Besides the unknown virus, the fluid of the vesicles may contain 

 various other bacteria; such as Kurth's streptococcus involutus, the 

 staphylococcus pyog. aureus, the micrococcus tetragenus, sarcinae, etc. 

 (Sanfelice). These pus-producing organisms may modify the later 

 course of the disease, and the occasional complications which develop 

 (deep ulcerations and suppurations, purulent inflammations of the feet, 

 mastitis, pyemia, etc.) may be attributed to their action. 



Anatomical Changes. Autopsies on animals which are 

 slaughtered during the development of the disease, or which 

 suddenly die, reveal as a rule, in addition to the characteristic 

 exanthema, only an acute catarrhal swelling of the mucous 

 membrane of the mouth, of the pharynx, and of the air pas- 

 sages, or there may also be present small hemorrhages on some 

 of the serous membranes, especially on the visceral layer of 

 the pericardium. In some cases however vesicles, or ulcerations 

 may be observed in the wall of the pharynx, on the mucous 

 membrane of the bronchi and esophagus, in the stomach (in 

 ruminants in the first three stomachs, IJhlrich), and in the 

 intestinal canal. The ulcerations may sometimes be covered by 

 a fine fibrinous deposit. 



Animals which die as a result _ of complications, reveal 

 severe suppurating processes, especially on the lower parts 

 of the extremities, which are frequently associated with caries 

 of the neighboring bones. There may also be found purulent 

 or ichorous inflammation of the joints, or metastatic abscesses 

 in various parts of the body, and acute degeneration of the 

 parenchymatous organs. In some cases a gangrenous pneu- 

 monia is the immediate cause of death, which results from 

 inhalation of saliva or food particles. 



If the animal dies suddenly in the stage of commencing 

 recovery, from the malignant type of foot-and-mouth disease, 



