462 DISEASES OF CATTLE. 



This vaccine, which is in the form of a brownish, dry powder, is 

 mixed with definite quantities of sterile water, filtered, and by means 

 of a hypodermic syringe the filtrate injected under the skin in front 

 of the shoulder of the animal. The inoculation is usually followed by 

 insignificant symptoms. In a few cases there is a slight rise of tem- 

 perature, and by close observation a minute swelling may be noted at 

 the point of inoculation. The immunity conferred in this way m^y 

 last for 18 months, but animals vaccinated before they are 6 months 

 old and those in badly infected districts should be re vaccinated before 

 the following blackleg season. 



The effect of the vaccine prepared by this bureau in preventing 

 outbreaks of the disease and in immediately abating outbreaks 

 already in progress has been highly satisfactory, and it is not to 

 be doubted that thousands of young cattle have been saved to the 

 stock owners during the eighteen and a half years in which the 

 vaccine has been distributed. More than 25,000,000 doses have been 

 sent out during this period, and from reports received it is safe to 

 conclude that more than 20,000,000 have actually been injected, 

 whereby the percentage of loss from blackleg has been reduced from 

 10 per cent, which annually occurred before using, to less than one- 

 half of 1 per cent per annum. With these figures before us it is 

 plain that the general introduction of preventive vaccination must be 

 of material benefit to the cattle raisers in the infected districts. 

 Moreover, there is every reason to believe that with the continued 

 use of blackleg vaccine in all districts where the disease is known to 

 occur, and an earnest effort on the part of the stock owners to prevent 

 the reinfection of their pastures by following the directions given, 

 blackleg may be kept in check and gradually eradicated. 



NECROTIC STOMATITIS (CALF DIPHTHERIA). 



[PI. XLIII.] 



Necrotic stomatitis is an acute, specific, highly contagious inflam- 

 mation of the mouth occurring in young cattle, and characterized 

 locally by the formation of ulcers and caseo-necrotic patches and by 

 constitutional symptoms, chiefly toxic. 



This disease has also been termed calf diphtheria, gangrenous 

 stomatitis, ulcerative stomatitis, malignant stomatitis, tubercular 

 stomatitis, and diphtheritic patches of the oral mucous membrane. 



History. — During the last few years farmers and cattlemen in this 

 countiy, especially in Colorado, Texas, and South Dakota, have 

 increasingly noted the occurrence of enzootics of " sore mouth " 

 among the young animals of their herds. Instead of healing, like the 

 usual forms, of themselves, these cases, if untreated, die. Careful 

 study of some of them has resulted in their identification with cases 



