io6 



MILK 



estimate by returning the number of leucocytes as so many per 

 microscopic field. This method is very inaccurate, since the 

 number will vary with the size of the microscopic field, and 

 especially with the thickness of the film, the latter being im- 

 possible to accurately control. The writer worked out the 

 following method, by which the cellular elements can be readily 

 and accurately enumerated in milk. 



Savage's Method 1 . The ordinary Thoma-Zefss blood-counting 

 chamber is employed. Direct counting of the cells is impossible 

 owing to the opacity caused by the large amount of 

 fat. One c.c. of the milk is accurately transferred 

 to a centrifugal tube (about 15 c.c. capacity) of 

 the pattern shown in Fig. 13, and freshly filtered 

 Toisson's solution 2 is poured in to almost fill the 

 tube. The two fluids are well mixed and then 

 centrifugalised for 10 minutes. The cream is well 

 broken up by a clean glass rod, to disentangle 

 leucocytes carried to the surface, and the mixture 

 centrifugalised for an additional 5 minutes. All 

 the fluid is then removed down to the I c.c. mark, 

 great care being taken not to disturb the deposit. 

 This can be conveniently and readily done by 

 means of a fine glass tube connected to an exhaust 

 pump. Theoretically, all the cellular elements 

 present in the original I c.c. of milk are now present 

 in the I c.c. of fluid. The deposit is thoroughly 

 well mixed (with a wire), and distributed through 

 the I c.c. A sufficient quantity is placed on the 

 ruled squares of the Thoma-Zeiss apparatus, and 

 the cover-glass put on. The number of cells is counted in a 

 number of different fields of vision, moving regularly from one 

 field of vision to another. The diameter of the field of vision is 

 ascertained before counting by drawing out the microscope tube 



1 Journal of Hygiene, 1906, Vol. VI, p. 123. 



2 This is the well-known indifferent solution used in blood enumerations. It does 

 not injure the cells, but stains them sufficiently to render them clearly visible. Its 

 composition is methyl violet 0*025 g rm - sodium chloride i grin., sodium sulphate 

 8 grms., glycerine 30 c.c., distilled water 160 c.c. 



\ 



1.C.C. 



Fig- 



