ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1089 



by putting a thermometer througli the hole in one of the lids into the 

 dry chamber and shutting off the regulator burner when the chamber 

 is warm enough. The temperature, as indicated by the thermometer 

 that dips into the water, is always a few degrees higher than that of 

 the dry chambers. When the thermometer in the water indicates a 

 temperature of 60^ C, the basins are warm enough to keep the hardest 

 grade of paraffin melted. The whole stands at a convenient working 

 height, about 3 ft. 8 in. 



Barrett's New Microtome. — Mr. James W. Barrett exhibited at 

 tbe last meeting of the Society a microtome which he had devised 

 (with the assistance of Messrs Swift Si Son) for the purpose of pre- 

 l)aring large sections of tissues imbedded in celloidiu, gum, paraffin, 

 or similar material, cutting under spirit, or (if necessary) under water. 



The machine is adapted to allow of the preparation of sections up 

 to 12 "5 cm. diameter, or even more, but Mr. Barrett has used it 

 chiefly to prepare sections of the whole eye, in which the parts are 

 maintained in situ. Fairly serviceable machines for these purposes 

 have hitherto been made by (amongst others) Katsch,* but the object 

 of the present construction has been to obviate the results of faults in 

 those previously devised. The chief improvements are (1) general 

 solidity and large size, (2) accurate raising mecbanism which gives a 

 definite minimum movement corresponding to a rise of "01 mm., and 

 (3) the support given to the knife at both ends. 



In using the instrument tbe imbedding mass is fixed to a plate or 

 tube carried inside the bath by the raising mechanism. If celloidin 

 is to be used, the mass is fixed to the cork-covered plate by simply 

 moistening both the cork and a flat surface of celloidin with etlier, and 

 then firmly pressing the two surfaces together in the air until the ether 

 has evaporated. The mass then becomes most firmly adherent to the 

 plate. The plate is then placed in the bath, which is filled with spirit, 

 and sections maybe at once cut. 



If paraffin or gum be used, tbe plate is replaced by an adjustable 

 metal tube which hohls the imbedding mass. The size of the plate 

 or tube can be made to vary almcjst indefinitely, so that if the manu- 

 facturer is informed beforehand, the machine can be adapted for the 

 preparation of sections of very great size. 



Bausch and Lomb Optical Go's. Laboratory and Student's 

 Microtome. — Tliis company have issued a modification of the 

 Schanze microtome, under the name of the " Laboratory Microtome." 



A second form, which they call the " Student's," is shown in 

 fig. ^5.5. It retains the main features of the first form, but is limited 

 in its adjustments. The base, curved arm, upright and V-sliaped beds 

 for tlie obj<ct-liolfler and knife, are made of one casting, thus insuring 

 ri^'idity. The verticul bed has a grooved slot its full lungtlu An 

 iifljustalile carriage to whicli the oljject-liolder is attached, slides 

 along the groove and can be fastened at any jxiint. The knife-slido 

 rciits on five points upon Prc^f. Thoma's plan. It has a spring 



♦ See this Journal, ii. (1882) p, 12G. 



