182 THE DISEASES OF DOMESTIC ANIMALS. 



we have already learned that neither gases nor chemicals have the 

 power of multiplication within themselves ; yet even in this case, mnl- 

 tiplicatiou of the inficiens must have taken place to have produced 

 infection, for Gerlach says that " only some twenty drops of the 

 condensed fluid was used for the inoculations." Yiborg, who lived 

 early in the century, could not well have discovered form-elements 

 in these fluids, and it is doubtful if the microscope which Gerlach 

 used in 1868 was equal to it. At least, he reports that none were 

 to be seen, and concludes that the infectious elements exert a chemi- 

 cal action, which was also Yirchow's opinion at that time. Nega- 

 tive experiments (which, however, have always but little value in 

 the face of positive, as the individual immunity peculiar to all spe- 

 cies must always be taken into consideration) have been made by 

 Ilertwig, Eegnault, and others, with reference to the expired air 

 causing infection by means of the lungs. Diseased hoi'ses were 

 caused to breathe into a canvas bag at one end, while healthy ones 

 breathed from the other, yet in these cases no infection took place. 

 These experiments are, however, only too abundantly contradicted 

 by daily experiences. 



The Blood. — Numerous experiments made with the blood of 

 glandered horses have shown it to be infectious. 



Schimming * gives the following resume upon the results of his 

 and other experiments : 



1. " Yenous blood from a glandered horse injected into the veins 

 of a healthy one causes glanders. 



2. " The quantity of infected blood injected appears to exert an 

 influence upon the duration of incubatory stadium ; the stage of the 

 disease in the animal from which the blood was taken may not be 

 without influence also. 



3. " Three months may elapse after the transfusion of such blood 

 before we can recognize any pathognomonic symptoms. This will 

 probably serve to explain the negative results which followed some 

 of the experiments of Viborg, Gerlach, and Hening ; that is, the 

 period under which the animals were kept in observation was too 

 short to allow the disease to develop. 



4. " The blood from glandered animals appears to have a less 

 intensive action upon healthy animals than the nasal discharge, and 

 secretions from wounded surfaces." 



5. " Transfusions with such blood in dogs, cats, and swine, gave 

 negative results." 



6. " The subcutaneous injection of six grammes of deflbrinated 



* " Ansteckungsfahigkeit d. Rotzblutes," Dorpat, 18T5. 



