ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



643 



and then the sections are soaked in a relatively large amount of water 

 to remove the gum. Evidently while soaking, staining, and trans- 

 ferring the sections, especially if they be of such an organ as the 

 lungs, there is every liability of their becoming folded or torn. This 

 may be avoided by staining the tissue in the mass as for dry 

 section-cutting, and then soaking in water to remove any alcohol, and 

 finally comidetely infiltrating the tissue in a thick solution of very 

 clean gum arabic. 



When ready to make the sections the well of the microtome is 

 filled with the thick gum and the tissue introduced at the proper 

 time as usual. Before cutting, the gum is cut away from the tissue 

 as in sharpening very bluntly a lead pencil, then as the sections are 

 cut they are transferred directly to the slide. After several slides are 

 filled, a drop of glycerin is added to each section and the cover-glass 

 applied. This is practically mounting in Farrant's solution. 



Apparatus for Injection— Fearnley's Constant-Pressure Apparatus. 

 — Very great variety exists in the forms of this class of apparatus. la 

 the majority of them the leading principle is the compression of the 

 air in an intermediate vessel by the entrance into it of a liquid falling 

 from a greater or less height according to the pressure required, the 

 air then acting on the injecting fluid in another bottle communicating 

 with the first. 



In the two following the intermediate vessel is dispensed with. 



Banviers * (fig. 108) has a syringe connected by an indiarubber tube 



Fig. 108. 



with the bottle contidning the injecting fluid, which is supported on 

 a retort-stand. A second indiarubber tube terminates in the canula. 

 Ludwvfe I (fig. 109 j acts by the fall of quicksilver drop by drop into 

 the vessel, A, containing the injecting fluid I. 



* Thaiihoffer'B ' Das Mikruskop uad soiue Auweudunjj,' 1880, p. 187 (.1 lig). 

 t Ibid., p. 188 (1 fig.). 



