Весьма интересен вывод Келлера о возникновении борзых собак, очень древней группы, центр происхождения которой находился в Древнем Египте. Борзые собаки упоминаются еще во времена Древнего Царства, когда они использовались для охоты на антилоп. Прародителем группы борзых Келлер называет эфиопского шакала - ' стройного, длинноногого и очень длинномордого зверя среднего размера. Затем здесь же Келлер упоминает, что египтяне держали ручных гиеновых собак, прекрасных выносливых бегунов, охотников на различных антилоп, хотя автор и исключает влияние гиеновых собак на борзых. От борзых, по Келлеру, прослеживается ряд к типичной гончей собаке.

Domestic dogs exhibit an extraordinary degree of morphological diversity. Such breed-to-breed variability applies equally to the canine skull, however little is known about whether this translates to systematic differences in cerebral organization. By looking at the paramedian sagittal magnetic resonance image slice of canine brains across a range of animals with different skull shapes (N = 13), we found that the relative reduction in skull length compared to width (measured by Cephalic Index) was significantly correlated to a progressive ventral pitching of the primary longitudinal brain axis (r = 0.83), as well as with a ventral shift in the position of the olfactory lobe (r = 0.81). Furthermore, these findings were independent of estimated brain size or body weight. Since brachycephaly has arisen from generations of highly selective breeding, this study suggests that the remarkable diversity in domesticated dogs' body shape and size appears to also have led to human-induced adaptations in the organization of the canine brain.

MR Image Analysis
Using Analyze (Biomedical Imaging Resource), each dog's brain was realigned to the hard palate, as per veterinary radiological convention [2]. A paramedian sagittal slice depicting the olfactory lobe at its most distinct was selected and the region of interest of the brain and olfactory lobe were manually traced. Only the supratentorial cerebral hemisphere was traced due to ambiguities in demarcation of the brainstem on sagittal imaging. Planimetric 2D estimates of cerebral size and olfactory volume based on these traced images were calculated using Analyze. Traced images were then saved in Portable Networks Graphic (.png) format and imported into Matlab (MathWorks), for calculation of the centre of mass of the brain (CoMbrain) and olfactory lobe (CoMOL).
We then established a longitudinal axis (LA), as the longest possible line drawn from the most rostral point of the frontal lobe to the furthest caudal point of the occipital lobe (Figure 2). The angle of deflection between the hard palate and LA was used to calculate pitch, in effect a measure of dorsal-ventral cerebral axis rotation.

Our study introduces two new observations about the organization of the brain of the domestic dog. Approximately 69% of the variance in overall pitch of the brain, and 66% of the variance in the relative position of the olfactory lobe, was explained by skull shape as revealed by cephalic index. Increasingly brachycephalic dogs were found a have a more ventrally rotated cerebral axis and a more ventrally shifted olfactory bulb position. Interestingly, these relationships appear to be highly sensitive to CI because rather than appearing beyond a critical threshold, they were found across a wide range of skull shapes and were independent of body weight or brain size.
Canine brachycephaly is purely a human invention. For example, to the best of our knowledge the cephalic index of the wolf (Canis lupus) approximates 51 to 52, whilst in our sample of domesticated dogs, ranged from 42 to 87. A complex interplay of breed pressures since canines began human cohabitation about 12,000 years ago [19]– including selection for behavioral, functional, and more recently, aesthetic traits – has led to their amazing physical diversity [9], [20]. Some have speculated as to whether this prepotent physical variation intimates a unique level of plasticity in the canine genome [21]. Added to this, no other animal has enjoyed the level of human affection and companionship as the dog, nor undergone such a systematic and deliberate intervention in its biology through selective breeding.
This diversity is no less prominent than in the wide variation in the shape and size of the canine skull. In this study, this variability was found to extend to the organization of the canine brain. We found a strong correlation between high CI and both cerebral axis rotation (ventrally at the anterior pole) and a ‘ventralization’ of olfactory lobe location. Our analysis suggested this was most strongly associated with skull shortening rather than loss of skull girth in increasingly brachycephalic dogs.
But how could skull shortening affect cerebral organization? Studies of human craniosynostosis [22], [23] and immature head banding [23] suggest that the development of brain shape and size is closely interrelated to the configuration of dura matter as well as the co-developing cranial vault. Changes to any of one of these factors can lead to changes in the others [22]. Differences in canine skull length resulting from artificial human selection pressures may have led to alterations in cerebral development most evident in brachycephalic versus dolicocephalic dogs. Specifically, rostral intracranial volumetric restriction during development of short-skulled dogs may explain the combination of axis rotation and olfactory bulb repositioning. Regodon et al (1993) also noted that reduced skull length in brachycephalic dogs gives rise to a more perpendicular development of the cranium relative to the facial axis [5]. These anatomical adaptations could hence represent a biological solution to a ‘space problem’. The olfactory bulb seems to have migrated to a potential space ventral to the orbital frontal cortex, thereby freeing the anterior pole for normal development of the frontal cortex. Alternatively, animals at the dolichocephalic end of the spectrum may have sufficient ‘spare capacity’ in the cranial vault to permit olfactory bulb development almost directly anterior to the frontal lobe. Either of these possible explanations relies on an evolutionary and developmental preference to preserve frontal lobe volume. Future studies could therefore directly compare frontal lobe morphology in brachy- and dolichocephalic dogs.
Because differences in cranial morphology across dog breeds were closely associated with major neuroanatomical changes, whether these also lead to differences in behavior is a major open question. We cannot yet infer whether the progressive cerebral reorganization found in more brachycephalic dogs have direct functional sequelae. Interestingly, brachycephalic breeds are not typically selected for scent work because of poor olfaction assumed due to crowding of ethmoturbinate bones. Our data suggests a second possible explanation related to anterior-posterior compression of the skull and repositioning of the olfactory lobe relative to the rest of the brain. More broadly, dogs with different skull shapes may behave differently [9], but this is not entirely consistent [24]. Improved behavioral measurement of sensory, motor and cognitive function in domestic dogs is therefore a high priority.
Skull-shape dependent changes in the position of the olfactory bulb also predict a fascinating consequence for the adult rostral migratory stream (RMS). The RMS is a track of neural precursors that originates in the subependymal zone of the lateral ventricles and terminates in the olfactory bulb, contributing to neural turnover in this brain structure in both rodents and humans [25], [26]. Whilst its functional significance remains unresolved, neurogenesis within the RMS is closely connected to olfaction [27], [28]. Given the predictable nature of differences in the location of the canine olfactory lobe based on cranial shape, our findings also predict a rule-based change in the spatial course of the RMS within the brain of domestic dogs. Histological confirmation of this prediction, and any possible behavioral implications for olfaction, are of intense interest for future research.
Finally, a potential limitation on our conclusions is that larger dogs generally tend to have larger brains and manifest a more dolichocephalic cranial morphology, and smaller dogs the opposite. The effects of cranial morphology on brain organization may therefore be confused with those of body and brain size. There are, however, two main reasons why this was unlikely to have been a major confounder in our study. Firstly, there were no significant differences in body weight or estimated brain size between our comparison groups. Secondly, since our study may have been underpowered in this respect, we also took care to control for body weight and brain size in our correlational analyses. So even after accounting for brain size or body weight differences, there was strong evidence for a correlation between CI and both cerebral axis and olfactory lobe position. The effects of skull shape on cerebral axis and olfactory lobe position therefore appear to be independent of body or brain size.
To further disambiguate these competing influence on canine brain organization, future research may also profit by studying those interesting dog ‘outliers’ which break the usual body size-cephalic index norm. These include dolichocephalic breeds with low bodyweight (such as the Italian greyhound), and brachycephalic breeds of high bodyweight (such as the Neapolitan mastiff). Use of high resolution 3D MR imaging as often used in human brain studies would also allow more accurate calculation of whole brain volume, as well as possible changes in lobar organization or grey and white matter distribution.
Overall, our findings suggest that the remarkable variability evident in canine morphology is also apparent in the dog's cerebral organization. We found strong and independent correlations between cephalic index and pitching of the long brain axis, as well as ventral positioning of the olfactory lobe. Further investigation of the inter-relationships between skull shape, brain organization and behavior represent fascinating directions for future canine research.