10 



but in no wav restrained. The importance of this fact will be apparent 

 a little later when we come to discuss the effect of acid broths. 



On the foiu'th day. in this alkaline beef broth. Ps. hyaeinthi showed 

 a small amount of yellow precipitate. On the 6th day there was less 

 precipitate than in tubes of acid beef broth I stock 2S6a) 11 days old. 

 but it was yellower. The clonding was so slight that a penholder was 

 easily visible l3ehind a thickness of two tubes. 



On the eleventh or twelfth day there was more of the yellow pre- 

 cipitate than on the sixth, but it was not copious. Rolling clouds were 

 \-isible on shaking, but no zooglce^e. There was no pellicle, but now 

 for the lirst time a feeble rim of germs was to be seen on the wall of 

 the tube at the surface of the fluid. Under a Zeiss hand lens ( X 6 

 aplanat) this rim appeared as a pale amorphous membrane thickly set 

 with a series of roundish colony-like aggregates, which were white or 

 yellowish, and which did not dissolve when shaken down into the fluid. 

 Four days Liter the largest of these colony-like bodies were distinctly 

 yellow, the smaller ones being white. On the twentieth day the fluid 

 was uniformly clouded; there was no pellicle. ?nd no ragged zooglce^e 

 were visible to the naked eye. The bright yellow prec-ipitate on the 

 bottom of the tube now covered a diameter of only 1 mm. The rim 

 of germs was broad and filmy. It easily jarred off in large fragments, 

 or as a whole, and f^ll to the bottom. It contained a great many 

 zooglcei?e set at regular intervals in what still looked under a X 6 Zeiss 

 aplanat like a homogeneous membrane. The upper, larger, and older 

 aggregates were decidedly yellow, and set so closely as to form a yellow 

 border on the upper rim of the ring, which was exposed to the air. The 

 lower, smaller, and younger zoogloe* on this ring were white, this 

 part being submerged or barely out of the fluid. [Subsequent observa- 

 tions showed that these white zooglce^e always became yeUow with 

 increasing age and size.] The greater part of the clouding was stiQ 

 attributable to individual germs, but some small zooglceie could now 

 be seen in it. especially when examined with the hand lens. Under 

 the compound microscope (Zeiss 16 mm. and 12 comp. oc.) the zooglceie 

 on the rim looked like small, closely set colonies on an agar plate, i. e., 

 they consisted of roimdish. colony -like bodies on a paler, homogeneous 

 looking membrane. Stained with gentian violet and examined under 

 high powers the homogeneous substratum was seen to ^^ composed of 

 slender rods, which were often in short chains of 6 to lii. or more seg- 

 ments, the individuals forming the chains being distinct and of the 

 same size and shape as chose not joined. 



On the thiity-third day there was a moderately abundant yellow 

 precipitate, and the color approximated Ridgway's canary yellow. 

 The fluid was less cloudy than k had been, but was still unifonnly so. 

 It was not turbid with zooglo?». but some small flecks were floating in 

 it. There was no pellicle, but an easily detached, pale, fragile, homo- 

 creneous rim of orerms. which was closelv set with small, roundish, uni- 



