428 AMOUNT OF A BIOLOGICAL SAMPLE 



greatest uniformity is achieved by continuous sectioning at con- 

 stant speed. The first section is always discarded, and, in order to 

 minimize the temperature effect of the intermittent cooling with 

 carbon dioxide as commonly practiced, it is particularly important 

 to discard the first section after cooling and proceed at once to cut- 

 ting before appreciable warming can occur. These difficulties have 

 been surmounted to a great degree by Linderstr0m-Lang and Mo- 

 gensen (1938), who devised a means of maintaining the entire micro- 

 tome at a constant temperature low enough to keep the tissue frozen 

 on the block, at the same time making possible the free manipula- 

 tion of the instrument and the sections. In addition they developed 

 a method to prevent undue distortion or curling of sections on the 

 knife edge. 



Linderstr0iii-Lang and Mogensen Method for Accurate Cutting 

 and Special Handling of Frozen Tissue Sections 



A cryostat large enough to hold a rotary microtome is arranged to 

 maintain a constant temperature of around —20°. The type devel- 

 oped by Linderstr0m-Lang and Mogensen (1938) is indicated by 

 Fig. 152. The cabinet is made of two layers of wood, an inner one of 

 22 mm. furniture board and an outer one of 10 mm. cross cut veneer. 

 A sloping lid is hinged to the front of the cabinet, and through two 

 openings {A and B), lambskin-lined leather gloves are attached. The 

 gloves are of a size to permit easy manipulation within the cabinet. 

 An observation window (C) consists of a fiat glass cell filled with 

 water, which is prevented from freezing by a small low-heat elec- 

 tric resistance coil fitted against it. An extra hole (D), which is kept 

 closed with a stopper, enables removal of sections from the cabinet. 

 The interior is illuminated by a lamp (E) which fits over a glass 

 window in the top. A wooden partition separates the interior into 

 a front and rear chamber, the latter being about half the size of the 

 former. The rear compartment, fitted with a well-insulated lid, is 

 arranged to hold dry ice. Two guide rails fixed on the fioor of the 

 front compartment serve to hold the microtome in position, and in 

 order to prevent the frosting of the microtome, an electric heater 

 capable of holding the microtome at 5° in placed between the rails. 

 A thermoregulator fits through the left side of the roof of the micro- 



