334 SUMMARY OF CURRENT RESEARCHES RELATING TO 



knife-snj^port, there is one of the rollers. By the adjusting-screws St the 

 whole apijaratus is so arranged that, when the knife-carrier is in motion, no 

 other friction occurs than that of the rollers on the strip hhh. 



The vessel is filled by screwing off the head Z. As the tube r acts as a 

 siphon, it is necessary when the cock is turned on to blow down the tube. 

 The stream of spirit should be directed at a right angle to the knife, and 

 about the middle of the object. This done, the object Oh by means of the 

 screw Jc is firmly grasped in the fangs of the object-carrier ; the correct 

 direction for the position of the knife is given to its surface by the screws 

 at /and/,, and then the axes of the fangs are tightened up by the levers 

 q and q'. If the height of the object is not quite correct, adjustment is 

 made by the screw m. By turning the screws s s the holder is fixed. 



V is a wheel with cranked axle JEw, and this by means of a catgut band 

 moves the knife. 



Microtome used at the Naples Zoological Station. — This instrument 

 in its improved form (figs. 87, 88, and 89), is described by Herr R. Jung.* 



(1) The knife and its carrier. — The knife, wliich is plano-concave, is 

 pushed into its holder a (fig. 88), and fixed by means of the two screws b at 

 both points. The holder is in its turn fastened to the carrier by means of 

 two bolts c, and these are screwed up by inserting the rod d in one of the five 

 holes (cf. fig. 87). If the knife is to rest on the carrier directly, the shorter 

 bolt is used ; if, on the contrary, the object to be cut is very long, it becomes 

 necessary to raise the knife, and one, two, or three metal plates having 

 been placed underneath, the long bolt is used. The choice of the screw 

 depends on the form of the object and the position of the knife. The latter, 

 in virtue of the construction of the holder, can be used in any position, and 

 along its whole length. For large objects of unequal texture, it is recom- 

 mended to place the knife as far as possible in an almost parallel position 

 (cf. fig. 88), and to move the carrier slowly and carefully. In this way siich 

 objects are cut to the best advantage. If, however, the object be small and 

 of similar consistence throughout, the knife may be placed in front and 

 the section made by a planing motion. The parafiin block which incloses 

 the object must be so arranged that the anterior and posterior edges of the 

 section are parallel, and also at right angles to the middle vertical plate of 

 the instrument ; in this way, with quick planing, the sections stick together, 

 forming large bands. 



Before the knife is sharpened or stropped it is fastened to the handle, 

 and a steel case is pushed up over its back and screwed up. In most 

 instances one turn on a good strop suffices, and this should be done without 

 any force. 



(2) The section-stretcher. — In its new form this can be used for any posi- 

 tion of the knife, and is easily applied thereto. The long rod e (fig. 88), partly 

 with the hand, partly by means of the two screws/ is accurately adapted, 

 parallel to the surface, and in such a way that it projects over the edge ; 

 it is then lowered by the front screw g, until almost in contact with the 

 knife-surface. For small objects the slender, for large, the thick rod is 

 used. If the sections are very bulky, the tendency to turn up must be 

 prevented by pressing lightly on the section with a spatula, &c., as it 

 appears between the rod and the blade. If the section-stretcher be pro- 

 perly arranged it works perfectly trustworthily, provided the sections have 

 no tendency to crumble. When the knife is placed obliquely, the paraffin 

 block is best shaped as a right-angled triangle, so disposed that the knifo- 



* Preis-Verzeichniss, 1886, pp. 16-9 (3 figs.). 



