57 



being transmitted through % the milled heads by a 

 rack and pinion or screw movement. If pecuniary 

 means will permit it, it is a most useful addition 

 and by it work can be done systematically and 

 with the assurance that every portion of the field 



Fig. 23. 



has been covered and withall with a degree of 

 comfort which must be experienced to be appre- 

 ciated. For instance, in a bacteriological or 

 urinary specimen, where one is searching the field 



