248 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



carrier thus varies directly with the degree of eccentricity of the 

 attachment of the connecting rod. The working of the micrometer- 

 screw is automatic and can be adjusted by means of a peg on the 

 knife-carrrier. The advantages claimed are : 



1. Mechanically ensured movement of the knife-carrier exclusively 

 in the course of the sliding track. 



2. Simplicity of construction without cogged wheels. 



3. Variability in the extent of the movement of the knife-carrier. 



4. Automatic working of the micrometer-screw. 



5. Adaptability of the apparatus to other sliding microtomes. 



Rotation Microtome.*- — P. Krefft has devised a microtome, named 

 by him " Herzberge," of which the knife (fig. 42) is the special feature. 

 This is semicircular in form with an outer cutting edge, and it rotates 



eccentrically round a selected point 

 lying somewhere in its diameter. 

 During such an eccentric rotation 

 the distance becomes constantly and 

 gradually increased between the ro- 

 tation point and the cutting point 

 of the advancing edge, which ad- 

 vances to just double the extent of 

 the eccentricity. The knife is fixed 

 to a holder on the top of a vertical 

 axis, on the head of which is a milli- 

 FlG - 42 - meter scale for the setting of the 



knife to the required eccentricity, 

 which should be equal to half the broadest diameter of the prepara- 

 tion to be cut through. The knife-holder grasps the whole back of the 

 knife, and so any elastic spring is avoided. Across this axis passes a 

 rod which can become fixed in the required position and serves for the 

 regulation of the automatic block-raising apparatus : during the half 

 of the revolution, in which the semicircular knife runs free, i.e. does 

 not cut, a lever fixed to the chief axis pushes the rod to one side, and 

 at the same time by means of a catch takes hold of and moves the 

 toothed micrometer-screw, and so causes the block to be raised. During 

 the second half of the revolution, in which the knife cuts, the lever is 

 out of reach of the rod. The whole is worked by a handle, which by 

 means of a cogged wheel acts on the chief axis. 



For the cutting of paraffin ribbons a straight-edged knife can be 

 substituted for the semicircular one. The advantages claimed for this 

 microtome are : 



1. The absence of elastic spring. 



2. The course of the knife is uniform and sure. 



3. The manipulation is easy. 



4. The sections are uniformly regular. 



Stebbins, J. H. — New and cheap Haematoxylin Stain. 



Journ. Kew York Micr. Soc. Annual, 1902, pp. 1-6. 

 „ „ Goldhorne's Double One-dip Bloodstain. Tom. cit., pp. 6-7. 



Zeitscb. wiss. Mikr., xx. (1903) pp. 7-11 (2 figs.). 



