94 OTIAPTEli VII r. 



Mechanical means may be employed. The simplest of 

 these is as follows : 



During the cutting the edge of the section that begins to 

 cuvl is caught and held down on the blade of the knife by 

 means of a small camel-hair brush with a flat point, or by a 

 small spatula made by running a piece of paper on to the 

 back of a scalpel. Or, which is much better, the section is 

 held down by means of an instrument called a " section- 

 stretcher." This consists essentially of a little metallic 

 roller suspended over the object to be cut in such a way as 

 to rest on its free surface with a pressure that can be 

 delicately regulated so as to be sufficient to keep the section 

 flat without in any way hindering the knife from gliding 

 beneath it. 



See the descriptions of various forms of section-stretchers, Zool. 

 Anzcig., vol. vi, 1883, p. 100 (Schtjltzb) ; Mitth. Zool. Stat. Neapel, iv, 

 1883, p. 429 (Matee, Andres, and Giesbkbcht) ; At-cli. mil;. Anat.. 

 xxiii, 1884., p. 537 (Decker) ; Bull. Sac. Belg. Mic, x, 1883, p. .55 (Fran- 

 cottb) ; The Microscope, February, 1884 (Gage and Smith) ; Whit- 

 man's Meih. m Mic. Anat., 1886, p. 91 ; Zcit. wiss. Mih., iv, 1887, p. 218 

 (Strasser) ; ihid., x, 1893, p. 157 (Born). The best are those of Mayer 

 and Bom. 



I find that Mayer's, beautifully made by Jung, works 

 admirably and is most valuable. 



Another plan is to allow the sections to roll, but to control 

 the rolling. To this end, the block of paraffin is pared to the 

 shape of a wedge five or six times as long as broad, the 

 object being contained in the broad part, and the edge 

 turned towards the knife (see Fig. 4). The sections are 

 allowed to roll and come off as coils, the section of the object 

 lying in the outermost coil, which will be found to be a very 

 open one- — indeed, very nearly flat. Lay the coil on a slide 

 with this end downwards, warm gentlj', and the part con- 

 taining the object will unroll completely and lie quite flat. 



Anile [Glandole duodenali, Napoli, 1903, p. 51) and 

 Vastaeini-Crisi (Mov. Zool. Ital., 1906, p. 164) lay a strip 

 of wet filter-paper on the block. 



A defect opposite to that of the rolling of sections is the 

 compression and the crumpling or puckering of sections, 

 indicating that the paraffin has been compressed by the knife 

 instead of being merely cut true by it. Such sections 



