The Action of Gravity upon Bacterium Zopfii. 305 



and come in contact with the glass surface, might branch and be 

 deflected back parallel to the ingrowing rami. 



Growth upon Agar. As stated above, we have never obtained a 

 -symmetrical growth in or npon this medium with or without glycer- 

 ine. The growth is that figured in photograph 10. It takes place 

 .slowly, and the margins are irregular, being formed of scattered 

 clumps of the bacterium. 



Growth upon Potato. Fig. 9 represents a potato culture ; the faintly 

 yellowish-white growth is observed to have no definite geotropic 

 arrangement. The potato, it will be observed, appears black ; this 

 has been produced by means of iodine, a method which we have em- 

 ployed with success in demonstrating delicate growths upon potato 

 surfaces. 



Growth in Broth. In broth abundant flocculi are formed. 



Growth in Animals. We have recorded how this micro-organism 

 was first discovered by Kurth in the alimentary tract of the hen ; 

 whilst in our own case it was present in very great abundance in the 

 pus of both the middle ears of the cat. It is just possible that in 

 the latter (present) case the microbe gained access to the ear by the 

 Eustachian tube, and therefore that the bacterium was originally in 

 the mouth. It is conceivable, therefore, that it may, in common with 

 the numerous other Cladothrix forms, be of more frequent occurrence 

 in the mouth than is suspected. We have, however, made no observ- 

 ation upon this point. We inoculated two rabbits subcutaneously 

 without result, and in another case the third of a test-tube full of a 

 broth culture was injected into the peritoneum with like lack of 

 success. These few experiments, however, prove little. 



The Action of Oxygen and Carbonic Acid Gas upon Bacterium 

 Zopfii. We have already brought forward sufficient facts to show how 

 sensitive this micro-organism is to changes of temperature. Fig. 11 

 represents a three days old growth in a test-tube kept in an atmo- 

 sphere of carbonic acid gas; there is simply thickening of the 

 original streak. Control test-tubes which were placed in oxygen at 

 the same time exhibited well marked symmetrical growths from 

 12 to 24 hours. Further, if the tube in which the growth had been 

 inhibited by the C0 2 were transferred to oxygen, a symmetrical 

 growth occurred, as in fig. 12. 



The Action of the Spectrum upon the Growth of Bacterium Zopfii.* 

 By means of a Zeiss sub-stage spectroscope a large spectrum was 

 projected through the micro-photographic camera and focussed upon 

 a Petri box of gelatine, across which a streak inoculation was made. 

 From our results so far with gelatine or agar we can only say that 



* For assistance in these experiments we are indebted to Dr. Fakirji Surveyor, 

 who, with one of us, is engaged in the study of the action of the spectrum upon 

 the pathogenic organisms. 



