1911.] Disintegrating Bacterial and other Organic Cells. 



63 



except that the pot, with its balls, steel cone, and outer cover, is mounted 

 horizontally between centres. 



On the spindle of the central steel cone D a semi-cylindrical mass of iron 

 or lead K is fixed, the weight of which has to be calculated for and pro- 

 portioned to the drag on the central cone, but must be such that when the 

 whole apparatus is rotated the weight is sufficient to keep the central cone 

 at rest. In practice this modification bas proved to be simpler than the 

 original model, the only objection being that it is not quite so easy to cover 

 the whole apparatus with an outside bell-jar as in the first described type. 



The following experiments were carried out with the apparatus 

 described : — 



Yeast. 



In order to ascertain the efficiency of the grinding under different 

 conditions, a series of experiments was performed with yeast. The yeast 

 cells being large, and their cell membranes being readily recognisable after 

 the cells have been crushed, it was possible to make an actual count of the 

 crushed and uncrushed cells after grinding. Fresh German yeast was used 

 and this was made into a smooth stiff cream with water for the purpose of 

 grinding. Films were made on glass slides at various stages of the grinds ; 

 these were stained with Loffler's methylene blue, and the counts made. 

 Controls of the unground yeast showed that practically all the cells were intact. 



The results obtained were as follows : — 

 I. Amount = 6 c.c. yeast cream. Speed = 700 — 750 revolutions per minute. 



(a) After 20 minutes' grind. Crushed cells = 597, uncrushed cells = 87. 

 Percentage of crushed cells = 87. 



(b) The same ground for a further period of 20 minutes. Crushed cells = 646, 

 uncrushed cells = 32. Percentage of crushed cells = 96. 



II. Similar to I. Total period of grind = 20 minutes. Examined at intervals of 

 5 minutes. 



(a) After 5 minutes' grind. Crushed cells = 63, uncrushed cells = 226. 

 Percentage of crushed cells = 21 -4. 



(6) After 10 minutes' grind. Crushed cells = 284, uncrushed cells = 343. 

 Percentage of crushed cells = 45. 



(c) After 15 minutes' grind. Crushed cells = 412, uncrushed cells = 113. 

 Percentage of crushed cells = 78. 



(d) After 20 minutes' grind. Crushed cells = 694, uncrushed cells = 59. 

 Percentage of crushed cells = 92. 



III. Amount = 12 c.c. of yeast cream. Speed 700 — 750 revolutions per minute. 

 Total period of grind = 30 minutes. Examined at intervals of 10 minutes. 



(a) After 10 minutes' grind. Crushed cells = 380, uncrushed cells = 326. 

 Percentage of crushed cells = 53 - 8. 



(b) After 20 minutes' grind. Crushed cells = 297, uncrushed cells = 195. 

 Percentage of crushed cells = 60. 



(c) After 30 minutes' grind. Crushed cells = 473, uncrushed cells = 109. 

 Percentage of crushed cells = 81. 



