10 THE CAUSE OF EUEOPEAN FOUL BKOOD. 



there is but one disease present in the condition which is being called 

 European foul brood is, therefore, still further confirmed. 



MICROSCOPIC STUDIES OF DISEASED LARWE. 



Eeturnino; now to the discussion of European foul brood in the 

 earlier stages, it should be emphasized that by a macroscopic exami- 

 nation alone it is not always possible to make a positive diagnosis 

 of the presence or absence of disease in a larva. During the very 

 earliest period of infection it is impossible from the gross examina- 

 tion alone to make a positive diagnosis of the presence of disease. 

 Such is to be expected. About the time the larva dies there is a 

 period at which one can not always be sure that the disease is present 

 from a macroscopic examination alone. Between these stages there 

 is a period in the course of the disease in the larvae during which it 

 is usually possible to make a diagnosis positive from the gross exami- 

 nation. Since a macroscopic examination alone is not always suffi- 

 cient for making a positive diagnosis, one looks naturally to a micro- 

 scopic examination for assistance. 



During the coui-se of the disease in the experimental colony the 

 microscopic picture presented in the examination of diseased larvte 

 changes markedly. To begin the microscopic study, it is well to 

 obtain the intestinal content as represented in «, figure 8. If a thin 

 smear is made of the white growtli-mas< of this content and stjiined, 

 it is found to consist almost entirely of forms represented in fig- 

 ure 9. 



This organism is the one that the writer referred to in an earlier 

 paper as ^' Bacilhts Y^ AH attempts to cultivate this new species 

 on artificial media have thus far l3een unsuccessful. Since consider- 

 able information has now been obtained concerning this organism 

 the specific name ^^ pluton'''' is now substituted for the "T" in the 

 term " Bae'dhis Y *' and the species will now be known as Bacillus 

 pluto7i. This organism is an unusual one and the classification has 

 not yet been definitely determi»ed. The generic term " Bacillus," 

 therefore, may, and probably will, be changed later. 



At the stage of the disease represented in a, figure 8, the majority 

 of the individuals of this new species in general appear in stained 

 preparations to be pointed at the ends (fig. 9). Some show both 

 ends rather sharply pointed, others show only one end so pointed, 

 the other end being rounded, while still others show both ends 

 rounded. The individuals having this general form vary much in 

 size. They are as a rule 1 [i or less in length, the breadth being 

 about one-half the length. Forms in pairs frequently occur in a 

 smear preparation made at this stage of the disease. These paired 

 forms vary markedly in size and shape. (See fig. 9.) Accompany- 



