and Laboratory Methods. 



2227 



was working in the zoological laboratory of Prof. Leuckart at Leipzig, where 

 they were then using the Rivet microtome. The unsatisfactory results obtained 

 with the wooden model led Dr. Brandt to have made by Leyser, the mechanician 

 of the university, the microtome which was long and widely known by the name 

 of Leyser, and to which I have referred above. Of this instrument I reproduce 

 the original figure, published by Brandt in Vol. VII of the Archiv fi'tr mikro- 

 skopische Anatomie, page 176. I still possess one of these early instruments, 

 which has seen a great deal of use. Its construction constituted a great step 

 forward. The essential addition by the Rivet type to what we had before had 

 was the substitution of the mechanical motion of the knife for the free-hand 

 motion, so that both object and knife were moved mechanically and therefore 

 with comparative precision. Perhaps the principal reason why this microtome 

 gained favor so rapidly is to be found in the fact that just before its introduction 

 the embedding of objects in paraffine had been introduced, and the microtome 

 was used chiefly for paraffine sections. The microtome itself may be described 

 as follows : 



It consists of a median vertical plate, on either side of which are two ways. 

 The way on the left hand side is inclined, being higher at one end of the instru- 

 ment than the other. On this way there runs a sledge that carries the object 

 holder which, as Dr. Brandt states, was made on the pattern of an American 

 patent clothes pin. This holder need not, I think, be further described. As the 

 sledge with the object holder and object would move along the way, it would of 

 course rise, the usual pitch being at the rate of 1 to 20. A scale on the micro- 

 tome enabled one to read off the thickness of the sections. The sledge would 

 move forward by hand and of course the position had each time to be read off 

 in order to make sure that the thickness of the section was that desired. The 

 way on the opposite side at the back of the figure was horizontal and upon it was 

 a second sledge, which carried the knife, the knife end being held in place by 

 means of a screw and clamp. In those days the knife was always placed in an 

 oblique position, even for paraffine cutting, and this is indicated in the illustra- 

 tion. It was not until later that 

 it was discovered that good sec- 

 tions of paraffine can be made ^ 

 with the knife at right angles 

 to the line of pull or draw. 

 From the Leyser microtome 

 have sprung numerous modifi- 

 cations, to some of which I shall 

 have occasion to refer later. 



The next important step in 

 the development of the micro- 

 tome was a combination of the 

 Ranvier type with the mechanical movement of the knife. The object holder 

 in this type, of which the Schanze microtome is perhaps the best illustra- 

 tion, is attached to a sledge or carriage which moves in vertical ways and 

 is raised in these ways by means of a micrometer screw with a very large head. 



Fig. 4. — Leyser-Brandt Microtome. 



