368 VETERINARY PATHOLOGY. 



the lympli nodes along the hihis of the spleen are invaded in 

 splenic lesions. 



Microscopic. — A small lesion is the result of a diffuse prolif- 

 eration of Ivmphoid and endotheloid cells and migration of 

 polymorph leucocytes. The proliferated cells may accumulate in 

 groups, thus producing nodules. In the beginning there is usu- 

 ally a well marked hyperemic zone around the cellular center 

 The cells constituting the central portion of the lesion later un- 

 dergo necrosis and about the same time the hyperemic zone 

 becomes less evident. A tibrous capsule may or may not en- 

 close the lesion, depending upon whether it is diffuse or nodular. 



In the nodular furm of the disease there is a proliferation of 

 fibroblasts in the tissue that was previously hyperemic. The 

 fibrfi1)lasts produce the capsule that characterizes nodular gland- 

 ers. In the older subsurface centers there is formed caseous 

 material and in the small centers calcareous particles. In sur- 

 face lesions, necrosis or fibrosis is evident. 



Diagnosis. — Mallcin is a filtrate obtained from a glycerinated 

 bouilliin culture of the Jiacteriun: mallei. Mallein is of diagnostic 

 ^■aluc (jnl)-. The cause of the reaction (jf glandered horses to mallein 

 is due t.i increased tissue action. The reaction noted in glanders con- 

 sists in a thermic disturbance, a swelling at the point of inocu- 

 lation, slift'ness in gait, general depression and there is usually 

 frei|uent urination. I'he temi)erature variations in glanders range 

 from '2° I", to .">' F. The maxinumi rise of temperature ustialK- 

 occurs in from ten to tA\'elve hours after malleination, though it 

 ma^- not ajipear until the eigliteenth hour after iniecti(in of the 

 mallein. The high temyierature eA'idenced in a mallein reaction 

 is maintained for a period of from ".M to (ii) hours. The swelling 

 is usually (|uite large and is verv scnsiti\-c. The lymphatic ves- 

 sels that are related to the swollen area become engorged and 

 present a knotted appearancee. The swelling characterizing a 

 mallein reaction persists for several davs. Stift'ness of gait may 

 be due largel}' to the disturbance induced bv the swelling at 

 the point of injection, but at least in some cases it is evident that 

 the stiffness of gait is not proportional to the size of the swell- 

 ing. Aside from stiffness the reacting animal has a dejected 

 appearance. The cause of freciuent urination is not known. 



Aggluti)iaiion. — Tlie bacterium mallei produces an agglutinogen 

 which causes the animal body to produce an agglutinin. A spe- 

 cific agglutinin is found in small quantities in the blood serum 

 of normal horses and in larger quantities in horses with gland- 

 ers. The agglutination test for glanders depends upon the 

 same principle, as that upon which the typhoid agglutination 



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