162 J. COSSAR EWART. 



introduced by Mr. Schafer. Through it I was able to keep 

 the same preparation under observation at the same tem- 

 perature for an indefinite time. Preparations cultivated in 

 the warm chamber were made by fixing a thin glass ring to 

 a glass slip by means of Canada balsam, Brunswick black, or 

 paraffin. The edge of this ring was covered by a thin layer 

 of olive oil, and the cover glass, with the drop of aqueous 

 humour containing the rods, was placed carefully over it. In 

 the same way the cover glass containing the specimen was 

 placed on the warm stage, but when the same cultivation 

 was likely to be under observation for a number of days it 

 was always advisable to fix the cover glass to the brass plate 

 by means of paraffin. 



On examining a small piece of spleen or a drop of blood 

 from the spleen of a mouse, which had just died from splenic 

 fever induced by inoculation, in a drop of fresh aqueous 

 humour from a rabbit, numerous motionless rods were seen 

 Ijing amongst the spleen tissue and blood-corpuscles. The 

 rods varied in length, the shortest being in length nearly 

 twice the diameter of a human red blood-corpuscle ; the 

 longer ones were two or three times the length of the shorter, 

 but when carefully examined they were almost invariably 

 seen to be in process of division into two or more segments. 



At first the bacilli were absolutely motionless, but in some 

 cultivations, after keeping the temperature at 33° C. for a 

 few hours, a great number of them began to move actively 

 about the field. By watching for several hours the bacilli 

 in a part of the field enclosed by spleen debris and blood- 

 corpuscles it was evident that they all closely resembled 

 each other, that they were alternately at rest and in motion, 

 and that some of them lengthened out into filaments. While 

 at rest they were not altogether without change, for clear 

 lines appearing across them indicated that they were in 

 process of division into segments. Sometimes a number of 

 rods ceased moving, and previous to lengthening out into 

 filaments, arranged themselves into patches of zoogloca 

 (Plate XI, fig. 19). 



When any particular rod was observed for some time it 

 might be seen first, slowly to move backwards and forwards, 

 then the movements gradually increased, until it wriggled in 

 a very active manner from one side of the enclosed space to 

 the other. Having continued active for some time, it would 

 either suddenly or gradually settle down again, as if exhausted, 

 into its former quiescent condition. I have seen rods 

 moving when with the No. X Hartnack they appeared from 

 half an inch to three quarters of an inch in length. 



