DIFFERENTIAL DIAGNOSIS 339 



larynx is inflamed. Also the subcutis when inflammatory 

 swellings appear on the skin. Schiitz found that in the brain 

 and spinal cord the arachnoid spaces are filled with a fluid 

 which is generally clear although it may contain leucocytes. He 

 reports one case in which the lateral ventricles contained a 

 large quantity (20 c. c.) of fluid. The other le.sions which 

 may be found depend upon the extent of localization of the 

 disease. Usually there are slight swelling of the spleen, small 

 hemorrhages in the intestines, under the serous membranes 

 and in the lungs, eyes and brain ; gelatinous infiltration of the 

 renal connective tissue and mesentery ; swelling of the lymph 

 glands ; j^ellowish serous exudates in the larger cavities of the 

 body and imperfect coagulation of the blood. One or all of 

 these changes may appear in a single animal. 



^257. Differential diagnosis. Influenza must be difi"er- 

 entiated from strangles and contagious pneumonia. The 

 differentiation between pleuro-pneumonia and influenza is 

 difficult only at the beginning, when merely general symp- 

 toms, such as fever, loss of appetite and weakness are present. 

 It .should be mentioned that the two diseases maj' affect the 

 horse simultaneously. When the skin is greatly swollen, in- 

 fluenza may resemble petechial fever, from which it can, how- 

 ever, very soon be distinguished by the absence of petechiae, 

 by the mildness of its course and its greater contagiousness. 

 In case of strangles, the lesions in the lymphatics may serve as 

 distinguishing characters. If abscesses are in evidence the 

 finding of the streptococcus of strangles would be quite con- 

 clusive. It would be positive providing Streptococcus equi 

 could. readily be distinguished from the pyogenic streptococci. 



With these diseases, a diagnosis, save in the more typical 

 forms, is difficult. Without a definite, recognizable, etiological 

 factor or other exact tests, a positive diagnosis in doubtful 

 cases can not be made. 



REFERENCES. 



1. LiGNiERES. Influenza or infectious pneumonia, the etiology of 

 ■ equine, /our. of Comp. Path and Therap. Vol. XI. (1898). p. 312. 



2. M'Fadvean. Influenza in the horse, what is it? Jour, of 

 ■Camp. Path and Theraputics. Vol. II. (1889). p. 105. 



