42 A MANUAL OF BACTERIOLOGY 



The filtrate thus obtained is the endotoxin, and is used to 

 immunise horses and other animals in the same manner as with 

 any other toxin ; it should be used as fresh as possible. The 

 amounts of a typhoid or cholera endotoxin employed for immunising 

 must at first be small, O2-0-5 c.c., as it produces considerable 

 disturbance on injection, and the amount is gradually increased. 

 After some weeks' treatment a dose of 20-30 c.c. may be injected. 

 When tests show that the serum has attained the necessary potency, 

 the horse is bled and the serum obtained and bottled. 



The endotoxins also possess immunising properties to a high 

 degree, and may be used as prophylactic or as curative vaccines ; 

 they markedly raise the opsonic index. 



Another machine has been devised by Barnard for disintegrating 

 bacterial and other cells. It is supplied by Messrs. Baker, of High 

 Holborn, and is depicted in Fig. 1, p. 41. 



The containing vessel consists of a phosphor-bronze body, A, in 

 which five hardened steel balls, B, are placed. The shape of the 

 containing vessel is such that when these balls are at its periphery 

 they accurately fit the inner side of the vessel. The balls are evenly 

 distributed round the vessel by means of a cage, c, and during 

 the time they are running this cage ensures that they are equi- 

 distant and do not collide one with another. 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. The vessel is closed by a screw cap, E, 

 through which the steel cone passes, and in which it is free to 

 rotate. Over the whole of this a metal cylinder, r, is placed, and 

 is screwed down, completely sealing the upper opening in the metal 

 vessel. In the top of this metal cylinder a steel bearing, G, is 

 placed, which has freedom of movement in a horizontal direction, 

 but is kept down on the top of the steel cone by the action of a 

 spring. It therefore follows that when this metal cylinder is 

 screwed down the steel cone is pressed on to the balls, and the balls 

 are in their turn forced out to the periphery of the metal pot. The 

 whole appliance is mounted on a cone, H, and a centre, I, which 

 are carried by two uprights attached to the base plate, J ; one end 

 of the shaft is attached to the electric motor. 



The grinding action is brought about by retarding the revolu- 

 tion of the central cone, D. This has been effected by mounting 

 on the spindle of the central steel cone, D, a semi-cylindrical mass of 

 iron or lead, K, the weight of which must be such that when the 

 whole apparatus is rotated it is sufficient to hold the central cone 

 still. 



