Grossman, 1953), and there is little information so far concerning its function

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52 J. Physiol. (I957) I35, 52-57 A SURGICAL APPROACH TO THE SUPERIOR CERVICAL GANGLION AND RELATED STRIJCTURES IN THE SHEEP BY THE LATE A. B. APPLETON* AND G. M. H.

1 52 J. Physiol. (I957) I35, A SURGICAL APPROACH TO THE SUPERIOR CERVICAL GANGLION AND RELATED STRIJCTURES IN THE SHEEP BY THE LATE A. B. APPLETON* AND G. M. H. WAITES From the Zoological Society of London, Regent's Park, and the Agricultural Research Council Institute of Animal Physiology, Babraham, Cambridge (Received 10 July 1956) The sympathetic nervous system of the ruminants is only briefly described in veterinary anatomical text-books (Ellenberger & Baum, 1943; Sisson & Grossman, 1953), and there is little information so far concerning its function in these species. As a method for the exposure and examination of the most cranial part of the cervical sympathetic nervous system, a lateral surgical approach to the superior (cranial) cervical ganglion of the sheep is described. METHODS AND RESULTS The surgical approach to be described has been successfully used for section of the cervical sympathetic nerve in chronic survival operations on nine Welsh mountain castrate male lambs (2-3 months old). Anaesthesia was induced with intravenous pentobarbitone sodium (Nembutal, Abbott Laboratories), average dose 29-5 mg/kg, and maintained with cyclopropane and oxygen after intubation with a Magill endotracheal tube. After the operation healing has always been by first intention and recovery uneventful, apparently without derangement of salivation, mastication, deglutition, rumination or eructation. The nictitating membrane of the operated side was relaxed but there was no apparent alteration in pupillary size, although, because the sheep has a slit pupil, any alteration was difficult to assess. Operation. The illustrations (Figs. 1-7) were prepared as a guide to the surgical approach to the superior cervical ganglion and were found in practice to be of great assistance. In these illustrations, in order to show the successive levels of dissection in the approach to the ganglion, certain structures, the jugular vein, the digastric muscle and the epihyoid bone, are represented as having been cut: in the actual operation they were only retracted. The skin incision was started over the zygomatic process at a point mid-way between the canthus of the eye and the base of the ear, and was continued parallel with the mandible to the level of the thyroid cartilage (Fig. 1). The thin cutaneous platysma muscle was then incised along the same line (Fig. 2), care being taken not to damage the external jugular vein which lies just deep to the muscle at the ventral end of the incision. The depressor auriculae muscle depicted in Fig. 3 was incised with the platysma muscle. After reflecting the cut edges of this muscle the parotid * Professor Appleton had completed the anatomical dissections and was responsible for the illustrations which form the basis of this paper before his death in April 1950.

2 SURGERY OF THE SUPERIOR CERVICAL GANGLION 53 gland, lying under fat in the dorsal area of the operative field (Fig. 4), and the external jugular vein became visible. The few vessels which pass caudally from the external jugular and internal maxillary veins were cut between ligatures, and the caudal and ventral borders of the parotid gland were then freed from underlying tissue to enable this gland to be retracted cranio-dorsally (Fig. 5). The common carotid artery could then be identified under fat, deep to the external jugular vein, and its cranial course to the point where it is crossed by the hypoglossal nerve could be identified. Here the artery passes deep to the digastric muscle, dorsal to which is the fan-shaped jugulo-hyoid muscle (Miller, 1948). This latter muscle was either wholly or partially cut through to enable retraction of the epihyoid bone. By retractingj the bone and the cut ends of the muscle using self-retaining retractors, the superior cervical ganglion, the cervical sympathetic nerve and the nerve from the superior cervical ganglion to the common carotid artery and related structures could be readily freed from the fat which surrounds them (Figs. 6 and 7). The operation was completed by suturing the cut ends of the jugulo-hyoid muscle, suturing the caudal border of the parotid gland into place and closing the skin and platysma muscle in layers. The operation from the skin incision onwards can be completed in less than 1 hr. Auditory meatus Approximate positionw,, of hyoid apparatus and larynx Fig. 1. The skin incision for the surgical approach to the left superior cervical ganglion. Line of incision Auditory meatus Fig. 2. Reflexion of the skin showing the line of the incision through the platysma muscle.

Auditory meatus glossopharyngeal (IX) nerve Fig. 4.

3 54 A. B. APPLETON AND G. M. H. WAITES Fig. 3. The superficial structures exposed by reflexion of the incised muscle. Auditory meatus glossopharyngeal (IX) nerve Fig. 4. Reflexion of the external jugular vein and branches and dissection of fat to reveal the common carotid artery; note that in the operation the jugular vein is not cut but is retracted towards the angle of the jaw.

The deeper structures visible after reflecting upwards the lower border of the parotid gland.

4 SURGERY OF THE SUPERIOR CERVICAL GANGLION 55 Fig. 5. The deeper structures visible after reflecting upwards the lower border of the parotid gland. Commron ca artery Fig. 6. Fatty layer revealed by reflexion of the cut ends of the digastric and jugulo-hyoid musclse and of the epihyoid bone: note that at operation, of these structures only the jugulo-hyoid muscle is cut.

5 56 A. B. APPLETON AND G. M. H. WAITES Ascending palatine artery Superior cervical Pharyngeal branch of ~ scle'uui-~#i Carotid artery branch of ~- Carotid artery sathervtica uguoncaotidoi nerve superior cervical ganglion was nerve Occipital artery Common carotid artery Fig. 7. The left superior cervical gangion and related structures exposed by dissection of overlying fat. The carotid artery branch of the IX nerve would appear to be the carotid sinus nerve (of Hering). DISCUSSION The conventional mid or paramedial cervical approach to the superior cervical ganglion, generally used in physiological studies, was attempted in sheep cadavers. It resulted in the exposure of the ganion at the bottom of a deep cavity formed by the surrounding tissues. Apart from the difficulty of manipulating the gangllon in this situation, the extensive dissection necessary for its exposure makes this approach unsuitable for chronic operations in the sh'eep. In man, the superior cervical ganglion is relatively superficial in position and is usually approached through a lateral cervical skin incision, after which only minimal surgery is necessary for its exposure. Although in sheep the ganglion is less accessible, it has been found most convenient to use the same approach as in man, when the ganglion is finally exposed by cutting through the jugulohyoid muscle which overlies it laterally. The surgical approach described here has been used successfully in a study of the degenerative section of the superior cervical ganglion by Hebb & Waites (1956) and by Waites (1957). In a series of animals in which the nerve section was successfully performed, there were no fatalities and the recovery was rapid and uneventful.

6 SURGERY OF THE SUPERIOR CERVICAL GANGLION 57 SUMMARY A lateral surgical approach to the superior cervical ganglion and related structures in the sheep is described. It is wished to acknowledge the generous assistance of Dr Catherine 0. Hebb at the operations. REFERENCES ELLENBERGER, W. & BAUM, H. (1943). Handbuch der Vergleichenden Anatomie der Haustiere. 18th ed. Berlin: Springer-Verlag. HEBB,C. 0. & WAITES,G. M. H. (1956). Choline acetylase in antero- and retro-grade degeneration of a cholinergic nerve. J. Physiol. 132, MILLER, M. E. (1948). Guide to the Dissection of the Dog, 2nded. Ithaca, NewYork: Edwards Bros. SissoN, S. & GROSSMAN, J. D. (1953). The Anatomy of the Domestic Animals, 14th ed. Philadelphia: Saunders. WAITES, G. M. H. (1957). Recurrent cardio-accelerator fibres in the right cervical sympathetic nerve of the sheep. J. Physiol. 135,

SCHOOL OF ANATOMICAL SCIENCES Mock Run Questions. 4 May 2012

SCHOOL OF ANATOMICAL SCIENCES Mock Run Questions 4 May 2012 1. With regard to the muscles of the neck: a. the platysma muscle is supplied by the accessory nerve. b. the stylohyoid muscle is supplied by