65 



under observation for an additional 24 days, during which time a great 

 change took place in one of them, the growth increasing tenfold. 

 This increased growth of the organism was due to no diastasic action 

 of its own, but to the diffusion of maltose or dextrin liberated from 

 the starch by some buried, slow-growing, white, starch-converting col- 

 onies, which originated from spores that found their way into the starch 

 during its preparation and which passed through the steamings 

 uninjured. 



The foregoing conclusion is also supported by the fact, already set 

 forth, that Pa. hyachithi grows well on a variety of crude vegetable 

 substances I'ich in sugar. That this feeble diastasic action partially 

 accounts for the feeble parasitism admits of little doubt. Probably 

 its feeble cytohydrolytic action and its strict aerobism are also restrain- 

 ing influences. 



AEROBISM. 



As already noted, th(> l)uried colonies of Ps. hyacinthi in plate cul- 

 tures grew slowly, and those deepest in the layer of agar or gelatin 

 remained smallest. In the stal) cultures also the bacteria gradually 

 faded out in the depths, making nuich the best growth near the surface. 

 The additional results bearing on the inability of this germ to grow 

 in the absence of free oxygen are thrown together in the following 



paragraphs. 



Fermentation Tubes. 



The form of tube used in my laboratory is that devised by Dr. Theo- 

 bald Smith and made by E. Greiner, of New York.' This, by reason 

 of its size and shape, the writer has found more satisfactory than sev- 

 eral other sorts he has tried. 



First is a table, which sets forth the results obtained with fermen- 

 tation tubes in 1897. The tubes were filled with distilled water con- 

 taining 1 per cent of Witte's peptonum siccum and 1 per cent of the 

 sugfar or other substance to be tested. 



^ The fermentation tube, with special reference to anaerobiosis and gas production 

 among bacteria. The Wilder Quarter Century Book, Ithaca, N. Y., 1893, p. 187. 



21T88— No. 28—01 5 



