102 MASTITIS OF THE COW 



a uniform smear of the material is made on the slide and 

 the organism is enlarged 550 times. 



The content of tubercle bacilli may vary distinctly, 

 however. There are cases where from 100-200 tubercle 

 bacilli occur in each field (Fig. 24), and also where the 

 tubercle bacilli are exceptionally few, one in every five 

 fields, one in a smear or even less, so that a microscopical 

 diagnosis is made with great difficulty or not at all. 



The milk can also contain other acid-fast rods besides 

 tubercle bacilli. They may be acid-fast actinomyces rods 

 in udder-actinomycosis or saprophytic acid-fast rods in pol- 

 lution of the milk. These rods may be mistaken for 

 tubercle bacilli or, on the contrary, tubercle 

 bacilli may be mistaken for these acid-fast 

 rods, especially in severely contaminated 

 milk samples. 



Of 841 milk samples examined micro- 

 scopically here in the High School, tubercle 

 bacilli were demonstrated in 155 cases, or 



FiQ. 24.— Tubercle . n ,^ i 



baciiu in milk sedi- ^g per ccut. oi the samples. 



ment. Ziehl(X550). %^, „ „ . ^ ... i 



The followmg errors were committed: 

 In two cases (0.24 per cent.) no tubercle bacilli were 

 found in obstinate udder-tuberculosis. In one case the milk 

 was examined again at fourteen-day intervals without re- 

 sults. The udder showed a slight distribution of tuber- 

 culosis without visible caseation in one anterior quarter. 

 The foci contained a few tubercle bacilli. The milk caused 

 tuberculosis in guinea-pigs. In the second case the milk 

 was only examined once. A possible error in staining is 

 not to be completely disregarded. The udder showed a few 

 tuberculous caverns containing loose caseous necroses which 

 were the size of a nut. In the necrotic areas a moderate 

 number of tubercle bacilli were found. Perhaps more 

 errors of the same kind were made, but they attained a very 

 small number, perhaps fifteen of the samples examined. 



