302 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



equivalent to 0*001 mm. The finest sections hitherto produced reach 

 only 0*002 mm. thickness. 



Since the first microtome was taken into use, a series of minor 

 improvements have been made. One of them consists in a clamp 



Fig. .53. 



Micrometer-screw for delicate sections. 



(fig. 54) for holding the object which can be turned round three axes, 

 and admits therefore of a very easy adjustment of the object in regard 

 to the knife. It was devised to meet the desire for occasionally 

 turning the object between two successive series of sections. 



The two metal plates h h form the jaws of the clamp. Between 



them is placed the cork 

 Fig. 54. which carries the speci- 



^ men, and the latter is 



fixed by turning the 

 screws g g. The three 

 axes are a, hh, and cc, and 

 round these the clamp 

 can be turned, a being 

 vertical, and bb and cc 

 horizontal. In all posi- 

 tions these three axes can 

 be made immovable by 

 the screws d, e, f. The 

 axis a is formed by the 

 vertical rod e (fig. 52), on the carrier supporting the clamp and object. 

 The details of the construction are partly new, and are very solid 

 and durable. Their arrangement is such as to admit of a division of 

 the circles in which the clamp can be turned. 



Another improvement has been devised by Mr. Jung. This is an 

 arrangement which regulates the movement of the micrometer-screw, 

 in such a way, that after a given number of divisions of the drum, a 

 spring registers to the ear and finger of the manipulator the number 

 of micromillimetres which the object has been raised. These 

 intervals can be varied within certain limits by a simple adjustment 

 comparable to a vernier. The construction of this apparatus is 



Clamp to be turned in three directions (as seen 

 from above). 



