ILLUSTRATIONS 



GENERAL STATEMENT 



All of the 113 figures are of adult or late larval Amblystoma tigrinum, except 

 figures 86B, 86C, 111, 112, and 113 of Necturus and figure 107 of Rana pipiens. 

 The indicated magnifications of the drawings show wide diversity in actual sizes 

 of the specimens due to two things: in the first place, the fresh specimens vary greatly 

 in size, and, in the second place, shrinkage during preparation may amount to as 

 much as one-fourth of the original linear dimensions. Figures 2-85 are original 

 drawings, and figures 1 and 86-113 are selected from previous publications, with 

 minor alterations in some of them. 



The internal structure of the brain of Necturus has been illustrated by sections 

 drawn at close intervals in the three conventional planes ('30, '336) and by many 

 drawings of detail in several other publications. The general plan of the brain of 

 Amblystoma is so similar to that of Necturus that comparisons are readily made. 

 The sections of Amblystoma have been under investigation for nearly forty years, 

 and the exigencies of the study and of publication have required concentration 

 upon particular topics rather than description of the brain as a whole, and no com- 

 prehensive atlas of sections has been prepared. It is the aim of this book to supply 

 a general view, but, unfortunately, the figures necessary to illustrate it are scattered 

 in many publications. Some figures of especial value for general orientation are in- 

 cluded here, and references are given to others in the literature. 



Three series of Weigert sections of adult A. tigrinum, prepared by the late 

 Dr. P. S. McKibben in 1910, were selected as standards of reference. These are his 

 numbers IIC, transverse. IC, horizontal, and C, sagittal. All were fixed in a formalin- 

 bichromate mixture, imbedded in paraffin, cut serially at 12 n, and stained on the 

 slides. These show minimum distortion of form, excellent histological preservation, 

 and brilliant stain of myelinated fibers, with decolorization arrested at a stage 

 which leaves all cell bodies clearly stained. The transverse series was chosen as the 

 type specimen, and this has been quite fully illustrated, though these drawings 

 were published at different times. To assist the reader who may wish to assemble 

 an atlas of this specimen, a list of all available figures of it was published ('35a, 

 p. 241), with serial numbers of the sections pictured, and to this list the following 

 numbers may now be added: 



Section 



98 Olfactory bulb. '246, fig. 5 



570. . . . Nucleus posterior tecti. '36, fig. 15 



595 ... . Cerebellum. Figure 91 



635 .... Posterior border of V nerve roots. Figure 90 



730 .... Level of IX nerve roots. Figure 89 



929 .... Anterior root of first spinal nerve. Figure 88 



956. . . . Calamus scriptorius. '446, fig. 4 



975 .... Commissura infima. Figure 87 



990 .... Nuclei of dorsal funiculi. '446, fig. 6 



Figure 2C of this work is the median section of the middle part of the brain stem, 

 reconstructed from this series of sections; and figures 1-4 of the paper of 1935 are 

 similar reconstructions, showing chorioid plexuses and blood vessels. 



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