434 



SUMMAKY OF CURRENT RESEARCHES RELATING TO 



use, the block and tissue are frozen by being immersed in powdered 

 ice and salt, then the block is secured in the clamp B, and sections 

 cut in the manner just described. The microtome, though essentially 

 a freezing one, may however be employed for cutting objects im- 

 bedded in paraffin. For carrying out this, the box shown in Fig. 86 

 has been provided. The tissue is to be imbedded in this box, and 

 when the paraffin has become quite cold, the box must be secured 

 in the clamp B and the tissue sectionized. 



" Yet another piece of apparatus belongs to this machine. It is 

 called an adjustable vice, and is shown in Fig. 87. It is the most 

 useful accessory, and there has long been a want felt for something 



Fig. 85. 



Fig. 86. 



Fig. 87. 



of its kind. It consists of a cylinder carrying at its upper end the 

 two jaws of a vice. One of the jaws is fixed, whilst the other, being 

 movable, may be made to recede from or approach to its fellow by 

 means of the screw, so that hard substances of different kinds and 

 various sizes may be securely fixed and held between the jaws, when, 

 the cylinder being inserted in the clamp B, sections may be readily 

 obtained. To the really working microscopist, this little appliance 

 will be found of infinite value in a thousand directions. The uses 

 of it are so obvious that no words will be wasted in describing them." 

 Though in this form, as in the others, the section knife, when 

 in use, is mounted on a frame, no absolute necessity for its adoption 

 exists, for the construction of the microtome permits of the use of 

 an unmounted knife as readily as one mounted on a frame. The 

 frame arranged has some advantages, particularly in retaining the 

 keenness of the blade for a considerable period (coming into contact 

 with nothing but the tissue) and in the confidence which it gives to 

 the inexperienced ojierator. On the other hand, it renders the dis- 

 engagement of the sections from the knife both a tedious and unsafe 

 process, and Dr. Marsh is strongly of opinion, as the result of a very 

 considerable amount of practical work, that in the hands of those who 

 by careful practice have taught themselves how to use it, a simple 

 unguarded knife is to be preferred to any mechanical arrangement 

 whatever. 



Bausch and Lomb's Standard Self Centering Turntable. — We 

 were unable to give at p. 284 any description of this turntable, but 

 the following has since been supplied by Mr. E. Bausch. 



