594 Transactions of the Society. 



no whole cells remain or that their number is reduced to a 

 minimum. 



3. The containing vessel in which the grinding action takes 

 place must be so effectually sealed that, during the process of dis- 

 integration, no cells have any opportunity of escaping. This 

 applies particularly when pathogenic organisms are being dealt 

 with. 



•4. The appliance must be such that an efficient cooling arrange- 

 ment may be adopted, and, if necessary, a temperature of — 15° to 

 — 20° C. maintained at the actual point at which the grinding 

 action takes place. 



5. The action presumably requiring to go on in metallic con- 

 taining vessels, it should be provided that the actual mechanical 

 disintegration of metal between the grinding surfaces should be as 

 little as possible. 



6. No material such as sand or kieselguhr, which were utilized 

 in some of the earlier forms of machine, should be added to the 

 material to be disintegrated, as it is necessary at a later stage to 

 remove these abrasive materials, a process which is not without 

 difficulty. They further have the effect in any case of tending to 

 raise the temperature during the grinding operations. 



The apparatus as designed is made in two forms ; in one 

 (fig. 72) it is mounted between horizontal centres, and in the other 

 (fig. 73) between vertical centres. In the former the grinding 

 action is controlled by gravity, and in the latter by electro- 

 magnetic means. 



The appliance consists essentially of a metal pot or vessel A, 

 in which a number of steel balls B are allowed to revolve. The 

 containing vessel may be made of phosphor-bronze, steel, or any 

 similar metal, but phosphor-bronze has been found the most 

 suitable ; it is the easier to work in the course of manufacture, and 

 owing to its toughness the surface does not disintegrate rapidly. 

 The steel balls accurately fit the inside of the containing vessel, so 

 that as the machine rotates they are in contact over nearly one 

 half their circumference with the inside of the vessel. A metal 

 cage C is made of such a shape that its prongs lie between the 

 balls, so that the latter cannot collide one with another when the 

 machine is rotating. Mounted at the centre of the metal vessel is 

 a steel cone D, which is of such a size that it keeps the balls in 

 their proper position in close contact with the periphery of the 

 containing vessel. This cone is an important part of the apparatus, 

 as upon it depends the pressure that may be exerted on the balls ; 

 and further as the result of its use the balls themselves have 

 freedom to slip if any additional strain is thrown on them or any 

 undue amount of material comes under their action. The con- 

 taining vessel is closed by a metal cap E, which screws down 

 hermetically sealing the vessel. A groove is made in the top of 



