. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 446 SYMPATHETIC NERVE. branches between the sympathetic and cere- bral nerves, they also regard it as probable that the greater number of the fibres in the communicating branches run peripherically. In the fish and bird they also found that the fibres of the communicating branches were di- rected partly towards the centre and partly to- wards the periphery. In small animals belong- ing to the class mammalia, such as the rat and mole, as well as in small dogs and cats, they found, on examining the communicating branches w
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 446 SYMPATHETIC NERVE. branches between the sympathetic and cere- bral nerves, they also regard it as probable that the greater number of the fibres in the communicating branches run peripherically. In the fish and bird they also found that the fibres of the communicating branches were di- rected partly towards the centre and partly to- wards the periphery. In small animals belong- ing to the class mammalia, such as the rat and mole, as well as in small dogs and cats, they found, on examining the communicating branches with the microscope as before, that the fibres passed both inwards towards the centre, and also outwards towards the peri- phery, and that the latter in many cases ex- ceeded the former. As already mentioned, there are commonly two branches of communication between each of the spinal nerves and the sympa- thetic in the higher animals. The one of these presents a white appearance, resem- bling more or less the ordinary nerves of the cerebro-spinal system; the other has fre- quently a more gray aspect, approaching in this respect the appearance of the sympa- thetic nerves. Sometimes the white cord presents the appearance of being composed of a white and a grayer portion running to- gether. As regards the minute structure of the rami communicantes, the whiter portion consists entirely of tubular nerve-fibres, both of the coarser and finer varieties . there are also not unfrequently present fibres which appears to be intermediate in point of breadth. In general the broader variety of fibres ap- pear to be more numerous than those which belong to the finer variety. According to Kolliker, the relation between them is much the same in point of number as in the pos- terior roots of the spinal nerves. The gray portion, as is stated by Todd and Bowman, contains a large proportion of fibres belonging to the gelatinous variety : in young animals it is often entirely composed of structures
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