294 MBNDOZA, RAMIREZ, AND ENRIQUEZ. 



halves, by making a cut through the longitudinal fissure, separating the 

 brain-stem at the middle. One-half of the brain is then cut into four 

 sagittal sections of the same thickness; the other half into four horizontal 

 sections of the same depths. Thinner sections may be made, yet they 

 are not desirable for beginners. 



Making the pulp. — Waste blotting paper that has been used is pulled 

 apart by hand ^ into small pieces and put into water to macerate, care 

 being taken first to wasli the mass two or three times. When the pieces 

 become soft they are reduced to a fine pulp with the fingers. The surplus 

 water is then squeezed out and the pulp thoroughly mixed with gum 

 which has previously been dissolved. 



Making copies of the contiguous surfaces of two adjacent sections. — 

 The most anterior coronal section is first taken, held on a mass of 

 cotton, the cut surface to be copied is then moistened with the preserving 

 fiuid and the onion skin paper immediately placed upon it. The struc- 

 tures beneath the latter are now plainly visible and their outlines can 

 be followed with a sharp pencil, thus making an exact copy of the 

 posterior surface of this section of the brain and the anterior surface 

 of the next. When this part of the work is finished, two pieces of 

 white paper with two of blotting paper are taken, the onion skin paper 

 placed over them and the external outline of the section cut through 

 them. The blotting paper is then set aside and two pieces of carbon 

 paper inserted between the pieces of white paper in such a manner 

 that when redrawn, the outline of the section on the onion skin paper 

 gives two copies on the white, representing the two adjacent surfaces, 

 one of this and one of the next section. By proceeding in the same 

 manner with the remainder of the sections copies of their surfaces can 

 be obtained. 



Model preparation. — The work is now ready for modeling. 



The two pieces of blotting paper, set aside in the last preparation, 

 which correspond to the anterior and posterior surfaces, for example 

 of coronal section number 2, are taken, the surfaces to be put in contact 

 with the pulp are painted with thick gum and between them such a 

 quantity of pulp, previousl}^ squeezed of its surjjlus liquid, is placed so 

 that its thiclmess is about 1 millimeter, for every centimeter, more than 

 the original section of the brain. The less the water and the more 

 homogeneous the pulp, the less will be the shrinkage of the model 

 in drying. The border is now made even throughout with fingers, 

 forcej^s, and probes; once all the sections are thus made they are 

 put together in their natural position and the rough outline of the 

 most important and deep fissures such as those of Sylvius and Eolando 

 and the longitudinal fissure are marked. Afterwards, taking each sec- 



^ Not cut with a scissors or knife. 



