STUDT or PELOMTXA PALUSTRIS. 383 



stage it appeared to he rigid, and was then much more resistant 

 to shocks of this kind. Having once secured the fact that the 

 bacilli did so fix themselves, I isolated several 2-jointed rods with 

 a few refringent bodies in a drop of water sealed from evaporation 

 by means of soluble glass, and these without exception fixed 

 themselves upon the bodies, but they did not grow, remaining quite 

 stationary as to size and number of joints. 



More advanced stages (three and five joints) obtained in other 

 fresh teased preparations are, however, seen on Pi. 36. figs. 6, 7, 

 rendering it evident that under normal conditions growth took 

 place after fixation, for no rod of greater length than the double 

 unit was ever seen to fix itself. Proof of this growth was finally 

 obtained by isolating 2-jointed rods and refringent bodies from a 

 fresh preparation in a hanging-drop of Mann's dilute solution of 

 egg-albumin, when growth occurred, and the rod under observation 

 attained 5 joints, but never developed fully, owing to the highly 

 artificial conditions. Three stages of such growth, as drawn at 

 intervals of 24 hours for three days, are seen in PI. 36. figs. 8-10. 

 A difficulty was, however, exjDerienced at this stage of the work 

 which unfortunately necessitated my transferring it to another 

 place. The floor of Prof. Weldon's laboratory was found to 

 vibrate so much that the commotion caused in a drop by a 

 passing footstep was sufficient time after time to dislodge bacilli 

 in an early stage of fixing. By the kindness of the Waynflete 

 Prof, of Chemistry I was, however, enabled to set up ray apparatus 

 for the hanging-drop cultures above described in a ground-floor 

 room of his department at the University Museum, on a balance- 

 table built up from the foundations, where the vibration difficulty 

 w^as entirely overcome and success attained. 



A number of cultures were now undertaken, but owing to the 

 difficulty of sterilizing egg-albumin, it was suggested to me to 

 use serum-albumin as the medium. Dr. "VV. Eamsden, of the 

 Physiological Department at the University Museum, kindly 

 provided me with some fresh sheep's serum, which I sterilized 

 by sucking it through a Muncke's filter by means of a vacuum- 

 pump into sterilized flasks which were closed with sterilized 

 cotton-wool. Two Pelomyxce, which had been kept hungry iu 

 clean water, in order to minimize as far as possible the danger 

 of contamination from their contents, were then cleansed 

 externally as far as possible by washing them successively in eight 

 vessels of sterilized distilled water. They were then thoroughly 



