ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 345 



best between 23° and 25° C. After the second sub-culture full growth 

 takes place in from four to six days. The sixteenth generation in 

 sub-culture retains full virulence. 3. " Liquide de Locke et serum de 

 boeuf." Dilute 1 c.cm. ox serum, heated to 56° C, with 9 c.cm. Locke's 

 fluid. Incubate at 35° C, after inoculation. After six days, sixty to 

 seventy spirocbsetes may be counted in each microscopic field. [The 

 thickness of the preparation is not stated.] Sub-cultures in this medium 

 grow badly, but it is an excellent one for conserving original cultures 

 from infected liver in vitro. Spirochaetes cultivated by these methods 

 resemble morphologically those found in the liver of the experimental 

 guinea-pig. They are pathogenic for this animal, and stain well by the 

 methods usually employed for the exhibition of cilia (e.g. Loeffler's and 

 van Ermenghen's stains and Fontana-Tribondeau and Eavaut-Ponselle 

 silver impregnation methods). 



(3) Cutting-, including- Embedding and Microtomes. 



Preparation of Rock Sections for the Microscope.* — C. H. Caflfyn 

 gives the following description of his method of making rock sections 

 for the microscope: — "The preparation of a rock section is not so 

 difficult a task as is generally supposed, and I propose to describe the 

 machine I use and the manner in which I carry out the work. The 

 machine is a home-made one, and consists essentially of a disk for slit- 

 ting pieces from the hand specimen and a lap for grinding. It can be 

 made by anyone who can use ordinary tools, and the total cost will be 

 well under twenty shillings. It will be seen from the illustration (fig. 2) 

 that the driving part of the machine is an old sewing-machine table, and 

 as the fly-wheel is rather light I have weighted it with lead pipe. After 

 inspection of various rock-cutting machines, I think it is better to have 

 the slitting-disk vertical rather than horizontal, as it is then possible to 

 put larger hand specimens in the holder. The slitting disk is attached 

 to a polisher's lathe-head, to be procured at any tool-shop, and is fitted 

 on to the attachment for holding the circular-saw. The disks are of 

 soft iron 6 in. in diameter, and about 5V i^^- thick. They must be 

 quite true, without buckle, or will not run well. The rock-holder is a 

 little complicated, but not difficult to make. It consists of a wooden 

 upright carrying a spindle, which in turn carries the holder. The 

 spindle is threaded 16 to the inch, so that one complete turn pushes the 

 rock forward over the edge of the disk ready for a second cut. The 

 holder consists of a piece of wood swinging on the end of the spindle, to 

 which it is attached by the ball-bearings from a bicycle pedal, which 

 allows free movement. Another piece of wood is screwed to this to 

 make one portion of the actual jaws, and tlie other piece is movable and 

 is clamped down on the rock by two screws with winged nuts. A chain 

 and weight keep the rock against the edge of the disk. The grind ing- 

 lap revolves horizontally, and is 8 in. in diameter and | in. thick. I 

 use cast-iron for these laps, but they can be made of lead or copper if 



* Journ. Photomicro. Soc, vi. (1917) p. 6-10 (2 figs.). 



June 9Mli, 1917 2 a 



