CARE AND UTILIZATION OF THE COLLECTION. 33 



secondary guide-lines sufficiently far outside of the proposed model not to conflict 

 with its casting. 



In order that these finished plates, which we call mold plates, may be kept in 

 exact apposition, they are piled in a rectangular corner made of plate glass (fig. 

 5). While this is being done it is necessary to cut certain artificial channels as 

 vents, so that the air will escape from the openings when the plaster is poured in. 



Fio. 5. Method of piling wax mold: /, baseboard; 2, perpendicular right angle corner; 3, glass plate; 4, wax mold; 

 6, vent; 6, galvanized iron wire bridge; 7, gate for plaster between parts of mold. 



It is also well to bridge loosely attached parts with copper wire, which is done by 

 heating the wire and laying upon the wax plates as they are being piled up. The 

 entire mass forms a mold which, to distinguish it from the others, is called a plate 

 mold. This is cast with plaster of paris, and after the plaster has set the wax is 

 removed by heating. Sometimes it is necessary to proceed farther and make a 

 break mold over the first cast, after which it is possible to make as many duplicate 

 casts as desired. In the above description the main outlines of this valuable 

 method of reconstruction, as now practised in this laboratory, have been given. 



Numerous general studies have also been made in embryometrics, in which 

 linear, gravity, and time values are considered. Furthermore, the technique 

 of gross anatomy has been applied to differentiate, by means of injection, the 

 arteries, veins, and lymphatics of the whole clarified embryo. Similar specimens 

 can be prepared to show the entire cartilaginous and bony systems. Thus many 

 embryos frequently are considered in a single publication, especially those illus- 

 trating causes of abortion and the production of moles and monsters. Attention 

 is therefore called to the numbers following the references in the appended list 

 of publications. These represent the catalogue numbers of the specimens studied. 



