ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



895 



longitudinally it must at the same time push the other slide S to the 

 side. For this purpose S' is provided with an oblique slit, in which 

 the tube h slides backwards and forwards. The latter is attached to 

 the plate a. The cylinder r serves for the reception of the object to 

 be cut, and by means of the micrometer screw can be raised by 

 hundredth parts of a millimetre, for which purpose a scale b with 

 index d is added. The slide S has also a transverse slit, so that it 

 does not come in contact with the tube h, and can move freely to a 

 certain distance. The attachment for the knife is on the slide S' ; 

 the stability of the knife m is ensured by securing it in two places, 

 first to the angle-piece h, which can be clamped in any position, and 

 with the slide S' ; and secondly by means of the screw m' which, 

 with the piece belonging to it, moves in a slit as shown in the figure. 

 The slide S' is moved by the handle g, and the oblique slit 

 enclosing the tube h (see Fig. 166) causes the slide S to move in the 



Fig. 166. 



Fig. 167. 



direction a a', and thus effects a " drawing " movement of the knife. 

 This movement is uniform if the slit is straight, as in the figure, and 

 it can be effected quicker or slower according as the slit is more or 

 less oblique. The drawing movement can also be accelerated during 

 the cutting process ; but in this case the slit must have a curved form, 

 as in Fig. 167. The whole microtome must, however, be broader, 

 although at the same time it may be shorter. By this arrangement 

 the knife is able to cut in any oblique position. 



In the microtome described the cylinder has a diameter of 25 mm., 

 amply sufficient in most cases, but capable of being increased. For 

 cases where it is preferred to use the knife with the hand, a circular 

 glass plate is added to the slide S'. 



Staining Bacillus tuberculosis.* — We have already described 

 Dr. Koch's original process for detecting this Bacillus and Dr. Ehrlich's 

 improvement upon it, as well as that of Dr. Van Ermengem.f Dr. H. 

 Gibbes, referring to the unsatisfactory nature of the first two pro- 

 cesses, says that the following simple process will bring out the 

 bacillus with ease and certainty. It takes but a short time to carry 



* 'Lancet,' ii, (1882) pp. 183-4. Brit. Med. Journ., No. 1137 (1882) pp. 

 735-6. 



t See this Journal, ante, pp. 385, 572, and 706. 



3 o 2 



