528 



SUMMARY OK CURRENT RESEARCHES RELATING TO 



and are then transferred to the 5 p.c. solution for one hour or more. In 

 the 5 p.c. solution the tissues are blocked on bits of wood or glass plate, 

 after which the blocks are passed through graded alcohols to paraffin. 

 The layer of agar round the tissues is rendered very firm by the alcohol 

 and prevents the material from being torn. The sections are very 

 satisfactory. 



If the material contain silicon it should be placed in water at 70° C. 

 for an hour, and then in 10 p.c. hydrofluoric acid for 12 hours. On 

 removal it is washed in water and treated as above. 



Accessory for Freezing- Microtomes.* — This invention of N. B. 

 Harman consists of a box of thin metal, the walls of which are prolonged 

 below the bottom of the box for the distance of a centimetre ; the box 

 is clothed in a jacket of felt. When sections are to be cut the chamber 

 is filled with a mixture of ice and salt, and the box placed on the glass 

 plate of the microtome, so that the specimen is enclosed in an atmosphere 

 below freezing point. This device saves both time and ether. 



Simple Freezing Microtome.f — W. J. V. Osterhout describes a 

 microtome suitable for botanical purposes. It consists of an iron stand 



Fig. 119. 



(fig. 110), which may be made from a piece of heavy T-rail about 8 in. 

 long with a width of 4 in. at the top. At one end it is cut away so as 

 to leave the two projecting arms, between which the freezing chamber/ 

 rests. This chamber is raised and lowered by means of the micrometer 



* Lancet (1905) i. p. 1505, 1 fig. 



t Univ. California Pub. Hot., ii. (1904) pp. 73-7 (2 figs.). 



