52 ANNALES DE L'INSTITUT PASTKl li 



appearanco of spirochaetos illuminated in tliis mannor is 

 naliirally familiar to ail workers on the subject and 1 shall only 

 refer to one or two points in connection willi it. In the iirst 

 place, one is struck by tjic contrast belween tlic high refracti- 

 lity and homogeneons appearance of young and vigorously 

 motile spirochaeles and tbe low refractility of many of those 

 which are moiionless, distorled in shape and prcsumably dead. 

 Another point which was sttidied with interest was Ihe so- 

 called « granule- shedding » phenomenon,described in connec- 

 tion willi Trepoîietna pallidinn and other Spirochaetes by 

 lialfonr and O'Farrel [9]. Jn tbe case of Spirochci'ta dutloni in 

 freshly sbed blood froni an infected mouse, kept under 

 conlinnous observation in a thermostat, it was sometimes easy 

 to detect highly refractile granules, apparently in the substance 

 of the spirochaete, coursing rapidly from end to end of tbe 

 rapidly rotaling organism, and even to observe tbe suddeii 

 extrusion of one of thèse granules from such a spirochaete. So 

 far, my observations were in accord with Ihose of Balfour and 

 O'Farrel, but I was surprised to find tbat, if one continued to 

 keept lie particular spirochaete and the particular granule which 

 it had extruded under observation, as was sometimes possible, 

 the granule apparently re-entered tbe boily ofthe spirochaete 

 and, once more, was seen to travel up and down it from end to 

 end. I hâve observed this séquence of extrusion and intrusion, 

 in the case of one spirochaete and one granule, no less than 

 seven times in succession within 3/4 of an hour and 1 am 

 inclined to think that the « granule-shedding » in this instance 

 was an optical phenomenon and could be explained on Ihe 

 assumption that a grain of blood-dust or haemoconia had 

 become involved in the vortex currents produced by the 

 rapidly rotating spirochaete and that it was, in this manner, 

 made to travel up and down the body ofthe spirochaete, accor- 

 dingly as the latter rotated first in one direction and then in 

 the opposite, as is their habit. It is of course quite possible 

 that the granules I observed were not of the same nature as 

 those described by Balfour and O'Farrell, but my impression is 

 that they were the same and that the phenomenon may bave a 

 physical rather than a vital explanation. 



Spécial attention was paid to the appearance of the granule- 



