THE DEVELOPMENT OF THE CEREBRAL VENTRICLES 



IN THE PIG 



CHESTER H. HEUSER 



Harvard Medical School, Boston, Massachusetts 



TWENTY-SIX FIGURES 



In this study of the cerebral ventricles of pig embryos three 

 methods have been employed — wax reconstruction, dissection, 

 and the making of minute casts. Wax reconstructions of the 

 ventricles have the advantage of large size. The volume of the 

 various cavities of the brain can best be estimated by immersing 

 portions of such reconstructions in water, and observing the dis- 

 placement. From these observations the actual size of the ven- 

 tricles can be readily calculated. But dissections and casts are 

 more accurate for showing details, as, for example, the neuromeral 

 grooves; and most of the drawings have been made from such 

 preparations. 



Brains of pig embryos measuring from 12 to 45 mm. were dis- 

 sected under the binocular microscope, with finely ground instru- 

 ments. Some of the dissections were designed to give a median 

 sagittal view of the right half of the entire brain. The embryo, 

 fixed preferably in Zenker's fluid, was held in a mass of cotton 

 wet with alcohol, between the thumb and index finger of the left 

 hand; and under a small stream of alcohol, a longitudinal cut was 

 made with a sharp safety razor blade. Very perfect cuts can 

 thus be prepared, such as will pass between the hemispheres and 

 thence backwards, sectioning the infundibulum, corpus mamillare 

 and other divisions of the brain almost exactly in the median 

 plane. Mesenchyma which covers the hemisphere, olfactory 

 lobe, or other portions which it is desired to expose, can be easily 

 removed with delicate needles and forceps. 



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