ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 431 



accordingly worked out the details of the adaptation which is shown 

 in Fig. 83. D represents the wooden bowl of the original form 

 altered to hold the ether freezing apparatus. A and B are the razor 

 frame and bowl-cover with the glass-plate top upon which the former 

 is moved. The central brass cylinder, instead of being solid, is 

 hollow, so that the ether spray may play up the inside and impinge 

 upon the lower surface of the brass-plate I, upon the upper surface of 

 which the material to be frozen is placed. In the figure, the hollowed 

 cylinder is seen to open below into the ether-containing chamber, 

 into the lower part of which also opens a horizontal tube, which turns 

 up at right angles and ends in a funnel-shaped extremity G, over 

 which screws a cap. 



In the centre of the bottom of this chamber is a circular aperture 

 closed by a piece of brass tubing, which passes up vertically to end 

 in a cone with a very small aperture, and having another small hole 

 in it towards the bottom. The lower end of this tube is plugged, and 

 through the plug E passes vertically a very fine tube, which is con- 

 tinuous below with the tube from the apparatus for pumping in 

 air. This consists of an indiarubber pump F, connected by a short 

 piece of tubing with a slightly distensible ball covered with 

 netting, and from the opposite side of which a piece of indiarubber 

 tubing passes on towards E. In the side of the large hollow cylinder 

 of the machine is inserted a small tube connected with a length of 

 pipe H for the escape of the spray after use. 



The method of freezing is as follows: — After the material has 

 been partially hardened, and the hardening agent removed, place it 

 on the brass plate I with a little gum mucilage ;* then unscrew the 

 cap G, fill the chamber with ether, replace the cap, and commence 

 pumping by pressing the ball F vigorously and rapidly in the palm 

 of the hand. Air will thus be pumped into the net-covered ball, from 

 which it will issue in a continuous jet along the indiarubber tube, 

 up the small tube, through the plug E, and again through the hole at 

 the apex of the conical-ended vertical tube, to pass straight up against 

 the under surface of the plate I. The rush of air thus produced 

 causes pressure on the surface of the ether, and also tends to produce 

 suction at the space between the small central tube and the one 

 which has the conical extremity, so that the ether passes through the 

 hole in the side of the latter tube, rises in the space between the two 

 tubes, and is forced as a jet of spray through the hole in the cone, 

 and so on to the under surface of the plate I. This is roughened in 

 the form of teeth for the purpose of presenting a large area to 

 be acted upon, and also to facilitate drainage. A great deal of the 

 ether drops down into the chamber, and is used again, but a little 

 passes out mingled with the air in such a finely atomized condition 

 that it seems impossible to collect it, and it is therefore conveyed 

 along the tube H to the external air. 



The advantages of the new form are that all mess with ice and 

 salt is avoided, that ether can always be kept at hand, and that 

 inhalation of the vapour is limited to the short period during which 



* If the material is quite fresh the mvicilage may be dispensed with. 



