118 PROCEEDINGS OF THE ACADEMY OF [1883. 



consistent, although objections may be raised to the author's 

 means of indicating position and direction.' 



My method of study was: (1) A careful examination of the 

 external features of the brain. (2) A series of very thin transverse 

 and longitudinal sections of the brain, the sections after staining 

 being carefully mounted in serial order. These series naturally 

 supplement each other and give a ver}- accurate idea of the gross 

 and minute structure. 



The technical process of preparing the brains was as follows : 

 The}' were hardened, after removal fi'om the skull, in a saturated 

 solution of bichromate of potash, the acid being subsequently 

 removed with alcohol of different densities. The brains were then 

 embedded in an egg-mass prepared by shaking the white and 3'olk 

 of egg together, with three drops of glj-cerine to each egg. This 

 mass was first stiffened around the brain by placing in a vapor of 

 alcohol, then hardened in absolute alcohol until ready for cutting. 

 Its advantages are that it closely embraces the brain, holding all 

 the parts together and becoming transparent in oil of cloves. 

 The section cutting was done with one of the large instruments 

 manufactured by Jung, of Heidelberg, which is far superior to 

 any other instrument of its kind now in use. 



External Structure. The brain of Amphiuma (Plate VIII, figs. 

 A and B) resembles that of Menopoma (figs. C and D) more 

 closely than that of any of the remaining Urodela. Its most 

 striking feature is that the component parts are, in the main, little 

 differentiated from each other, giving the exterior very much the 

 simple character of an embr^'onic brain. This is especially true 

 of the Di-, Mes- and Epencephala. The vertical longitudinal 

 section (fig. H) shows that the construction of the interior is 

 equally simple. The brain flexure is apparently slight. The 

 brain is also extremely small in proportion to the body, and has 

 a narrow, elongated form ; a remarkable feature is the diminutive 



' The following are some of the terms employed and their synonyms: 

 RMnencephalon, olfactory lobes ; Prosencephalon, including the cerebral 

 hemispheres and their cavities (procalice); Diencephalon, including the 

 thalami optici, the infundibulum, the pineal gland, etc., and the dia- 

 coelia or third ventricle ; Mesencephalon, including the optic lobes, the 

 crura cerebri and mesocalia or iter ; the vahula, or valve of Vieussens ; 

 Epmcephalo>i or ceTehellum] Metencephalon, medulla oblongata, and roof 

 of fourth ventricle. 



