Datasets -> The Brain of the Dog in Section, Singer/Leedle

[ Canis lupis General Info ]

The following text is excerpted from A Digital Edition of the Brain of the Dog in Section, available for download here.
Preface to the digital edition

It is a great pleasure to bring The Anatomy of the Dog Brain in Section by Marcus Singer into the 21st century. The original print edition was published in 1962, and has been out of print since then . It is a work of extraordinary quality and remains the best atlas of the canine brain anatomy available. Print copies are scarce and they show their age. The dog brain atlas needed saving. With this digital edition researchers and anatomists will no longer need to rely on reference library copies or copies inherited from colleagues. No one will need photocopies. Now anyone who “dumpster dives” to recover a retiring colleague’s copy will do so only because he/she wishes an original print edition and perhaps values the coffee stains which may adorn it.

This digital edition began in 2000 as a scan of a library copy. At the time, we were getting into neurotoxicology and needed neuroanatomy references to locate specific brain regions, nuclei, and fiber tracts. Like others, we were unable to purchase a canine neuroanatomy text so we settled for a borrowed library copy of Dr. Singer’s book. Luckily, we had an over-sized scanner available as the pages of the original text are 12.25 x 14.5 inches in size.

Surface Drawings
5 drawings

Traverse Plates
Dataset Id: 167
49 plates
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Horizontal Plates
Dataset Id: 168
28 plates
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Sagittal Plates
Dataset Id: 169
42 plates
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Notes on the brains, plates, and labelling

The Brains

The sections reproduced in the book were obtained from the brains of three disease-free beagle dogs of the same litter, aged five months, raised at the Virus Research Laboratories of Cornell University.

Each brain was sectioned in one of the three planes: horizontal, sagittal, and transverse. The dogs were anesthetized by intraperitoneal injection of Nembutal solution and then were perfused through the heart with a physiological saline solution followed by a solution of 10 per cent formalin. The brains then were removed, immersed in a solution of the same strength of formalin for a few weeks, dehydrated in graded alcohols, and slowly infiltrated with celloidin. The embedded brains were cut at 35 microns and the sections numbered consecutively. Selected sections were stained by the iron-hematoxylin method of Loyez for myelin sheaths after mordanting in alum of iron (Bertrand). Adjacent sections, which alternated with those stained for fibers, were stained for nerve cell bodies according to the cresyl violet method of Bielschowsky-Plien (Bertrand). Loyez sections are more useful for studying overall detail than sections stained by the Nissl method, and the present atlas is confined to sections stained for fibers. Indeed, nuclei, for example, of the thalamus often can be distinguished more clearly in such sections. However, constant reference has been made to sections of the cresyl violet series in locating nuclear groupings in Loyez sections.

During dehydration and embedding, the brains shrank to about three-fourths to two-thirds of the size of the fixed brain. The sections were numbered consecutively: the sagittal sections, from left to right; the horizontal sections, from ventral to dorsal; and the transverse sections, from rostral to caudal. The orientation of the sections corresponded closely to the desired plane. However, the sagittal sections were tilted about 1 mm from the true plane so that the midline section lies approximately in section number 575 (plate 59) for the medulla but in about section 605 for the rostral part of the brain stem. The transverse plane corresponded to a cut from the posterior commissure to the caudal extremity of the mamillary bodies (see transverse section 826, plate 35). Since the brain stem of the dog, unlike that of the human, is flexed only slightly at the mesencephalon, reorientation of the embedded specimen was not required, and the sections of the upper and lower brain stem deviated only slightly in direction from one another. The bilateral orientation of the transverse sections diverged only a little from the true orientation, the left being slightly more rostral than the right. In the case of the horizontal sections, a plane was chosen cutting through the anterior commissure rostrally and the decussation of the trochlear nerve caudally (see section 383, plate 114, Commissura anterior and Decussatio nervorum trochlearium). The bilateral orientation of the horizontal plane was tilted slightly so that the left side was cut a little more deeply than the right (for example, see section 456, plate 110, Nucleus corporis geniculati).

The Selection of Sections

Sections spaced at suitable intervals were selected for full reproduction in the atlas. The selection included 49 transverse sections, 27 sagittal sections, and 28 horizontal ones. In addition, 15 of the most medially placed sagittal sections were further enlarged and the enlargements are reproduced in the book. Consequently, the atlas consists of 119 plates of sections and 5 drawings of surface topography.

In the sagittal series, successive sections are separated in most cases by an interval of 10 (approximately 350 microns) except in certain regions. The most medial section is numbered 595 (plate 55) and the most lateral, 265 (plate 96). The spacing permitted visualization of all major structures. In the exceptions, the interval of separation between successive sections was reduced or increased. In the former instance, the interval from 475 (plate 83) to 485 (plate 77) also included sections 478 (plate 81) and 482 (plate 79) in order to show rapidly changing detail and to label the great profusion of structure that could not be accommodated in fewer sections. In the latter case, the most lateral sections, which showed little change in the 10 sections lateral to section 435 (plate 88), generally were spaced at intervals of 30 and 20 sections. In the enlargements of the 15 most medial sections, the brain stem was magnified further and cortical structures were largely omitted, a procedure adopted previously in the atlas of sagittal sections of the human brain (Singer and Yakovlev). The enlarged photographs of the brain stem served to clarify some of the detail and to multiply the space for labeling. Such special enlargements were employed for slides 595 (plate 55) to 475 (plate 83), inclusive.

The horizontal sections were also arranged in intervals of every tenth section, except in the most dorsal and ventral regions where the spacing was increased. In some instances, for one reason or another, the section was inadequate for reproduction, and therefore an adjacent one was substituted, thus introducing a disparity in the number sequence.

In the case of the transverse sections, the spacing between successive sections is in most instances about 20. In a few instances, the interval was less and at the rostral or caudal extremes was as great as 40 or 50.

The serial number of the section is recorded at the top right of each plate. Consequently, the distance of each section from any other of the same plane can be calculated by the reader, since each section is about 35 microns in thickness. For example, in the sagittal series, the interval between section 465 (plate 85) and the midline section 595 (plate 55) is 130 times 35 microns or approximately 4.5 mm.

Labeling Techniques

All labeling was done on a transparent paper overlay and then transferred in final form to a cellulose acetate overlay. The structures were labeled directly with lead lines, and the terms were abbreviated in a standard and simple way. The method of direct labeling was used in preference to symbols in order to preserve the beauty of the sections and to facilitate the identification of structures by the reader. Because of the wealth of structure to be identified, this method precluded complete labeling of each section. Consequently, most structures are not identified on every plate in which they occur but instead are labeled on alternate or occasional plates.

When a structure was labeled on a number of plates in one of the planes of section, the label generally was placed in a similar position on each plate for the convenience of the reader. Finally, it should be noted again that the sagittal sections were taken from the left side. However, in most medial sections the caudal part of the brain stem included part of the right side because of the orientation of the block during sectioning. Whenever right-sided structures are shown, (R) is affixed to the term.