168 



BACTERIOLOGY OF THE EYE 



resembled that of Morax very closely in appearance, but was slightly 

 smaller. Comparison of Petit' s figures, which are here reproduced 

 (Figs. 25 to 28), shows that the Morax- Axenfeld organism in cultures 

 more often shows longer forms. These really are involution forms which 

 occur more readily in the less resistant Morax- Axenfeld type, but do not 

 constitute a constant differentiation. Much more commonly it is im- 

 possible to distinguish in fresh cultures between Petit's and the Morax- 

 Axenfeld Diplobacillus. I have often been convinced of this. We can 



merely say that in the 

 Petit type the double 

 form is more constant 

 and longer retained. 



A special character- 

 istic of the Petit type is 

 that it grows very readil}' 

 on common media at 20 

 to 37 C. 



Petit states that on 

 agar thick, round, grey 

 colonies develop, which 

 are less prominent than 

 those of the Morax- 

 Axenfeld type, and have 

 no central elevation. 

 This latter differentiat- 

 ing point, which is shown 

 in Petit's photographs 

 here given (Figs. 27 and 



28), has been shown by MacNab's investigations in my laboratory not 

 to be constant. The central elevation may be absent entirely in the 

 Morax- Axenfeld Diplobacilhis, and can often be seen in the Petit type. 

 Coagulated serum is freely liquefied by the Petit type, as also is 

 gelatine at 22 0. At 15 C. the liquefaction is slower. It grows rather 

 badly in simple bouillon ; milk is not coagulated ; on potatoes a 

 creamy, light yellow scum grows. It is an obligate aerobe. At 

 50 C. the bacillus remains alive for a quarter of an hour ; at 55 C. 

 it is killed in the same time. Kept at 12 C. it can still be propagated 

 after ten days. For the usual laboratory animals it is not pathogenic. 

 MacNab alone obtained a slight hypopyon-keratitis in rabbits. 



Petit considered that the important distinctive characters of this 

 type were its growth upon ordinary agar, and especially its power of 



FIG. 25. MORAX- AXENFELD DIPLOBACILLUS. 



x 800. 

 Serum-agar culture, showing many filaments. 



