120 THE AMERICAN MONTHLY [Apr., 



step is accomplished. Especially is this true of serial sectioning 

 when the disarangement of the sections renders the slide al- 

 most worthless. In Lee's compilation of microscopical methods, 

 " The Microtomist's Vade-Mecum," there are about a dozen 

 different processes given for fixing paraffin sections to the 

 slide. These processes ftiU into two natural divisions, those 

 fitted for material stained in toto and those fitted for sections to 

 be stained on the slide. Of those belonging to the second group, 

 only a few admit of the use of both watery and alcoholic stains, 

 and in most of them heat is aa essential part of the process. 



Many of the methods involve a previous coating of the slide 

 with a substance that has to dry and be again moistened before 

 the sections can be arranged upon it, such as collodion, shellac, 

 or a gum-preparation. Some are useful for temporary slides, 

 while in others the intricacy of the process greatl}' increases the 

 chance of error, and adds to the time required for the work. 



There are no methods given in Lee's work of an earlier date 

 than 1880. One of the oldest is the Shellac Method, now no 

 longer used. Schallibaum's collodion also is best fitted for 

 bulk-stained objects. A slide is coated with a thin, even layer 

 of one part of collodion to three or four volumes of clove or la- 

 vender oil. The sections are arranged and the slides heated 

 over a water bath for five to ten minutes, or over a lamp for a 

 shorter time, till the oil has evaporated. Gage and Summers 

 use a pure collodion coat on the slide which is rendered adhes- 

 ive by clove oil or ether-alcohol. There are many gum methods, 

 but some forbid the use of watery fluids, and others are not 

 fitted for alkaline stains. 



Lee recommends Mayer's albumen for use with sections that 

 have to be stained on the slide, and says that he has found it 

 to be absolutely reliable. There is no need to describe so well- 

 known a method, the principle is the coagulation of a thin 

 layer of albumen by the use of heat. It is just at this point 

 that the element of uncertainty comes into the process ; much 

 heat will injure the tissue, and in avoiding this danger there is 

 a great probability of applying too little heat to coagulate the 

 albumen. 



Among other methods given b}^ Lee is one recommended b}' 

 Strasser, (Zeit. f. wiss. Mikr. , IV. 1. 1887, p. 45). It consists of 

 coating the slides thinly and evenly with a mixture of two 



