IMBEDDING METJIOD.S. 91 



bilrglscheii Mmeiimvereins, Bd. xix. Heft 1, p. 1 (Kolozsvar, 

 1897, A. K. Ajfcai). 



For honiurj knives see Ssobolbw, Zeit. wins. Mik, xxvi, 1909, p. 65 ; 

 Lbndtai, ibid., p. 203 ; Funck, ibid., xxvii, 1910, p. 75. 



Very large objects are best cut with the slanting knife, 

 and so are all objects of very heterogeneous consistency, 

 such as tissues that contain much chitin or much muscular 

 tissue ; and better with a slowly working sliding microtome 

 than with a quick-working Rocker or the like. Soft masses 

 such as gelatin or celloidin cut wet, can only be cut with the 

 slanting knife. The slanting position causes less compression 

 of sections than the transverse one. It has the defect of 

 producing rolling in paraffin sections more easilj^ than the 

 transverse position. The latter is the proper position for 

 cutting ribbons of sections from paraffin. 



By the lilt of the knife is meant the angle that a plane 

 passing through its back and edge makes with the plane of 

 section : or, practically, the greater or less degree of eleva- 

 tion of the back above the edge (it is not to be confounded 

 with the inclination of the long axis of the knife to the 

 horizon ; any accidental inclination that this may have is a 

 matter of no moment). 



The question of the proper tilt to be given to the knife 

 under different circumstances has been investigated by 

 Apathy, loc. cit. supra. He concludes — (1) The knife should 

 always be tilted somewhat more than enough to bring 

 the back of the under cutting-facet clear of the object. 

 (2) It should in general be less tilted for hard and brittle 

 objects than for soft ones ; therefore, cwteris paribus, less for 

 paraffin than for celloidin. (3) The extent of useful tilt 

 varies between 0° and 16° or occasionally 20°. (4) Exces- 

 sive tilt causes rifts (longitudinal) in the paraffin, also 

 furrows that in bad cases split up the section into narrow 

 ribbons. It also makes sections roll. Also it may cause 

 the knife not to bite, thus causing sections to be missed. Or 

 it may give an undulatory surface to the sections, owing to 

 vibrations set up in the knife, which may be heard as a deep 

 humming tone. Further, I would add, excessive tilt may 

 cause the knife to act as a scraper, carrying' away portions 

 of tissue bodily from their places. Excessive tilt may often 



