FIELDS H-1 and H-2 

 Columns 29, 30, 31, 

 32, 33, and 34 



2 ID Eyelid 



2 IE Conjunctiva 



2 IF Nictitating membrane 



133 Optic nerve 



971 Extrinsic muscles of the eye, in to to 



21G Ocellus 



21H Compound eye 



22 Ear; tympanal organ 



221 External ear, in toto ; pinna (auricle) and external auditory canal 



222 Tympanic membrane (ear drum) 



223 Middle ear, in toto 



224 Eustachian tube 



923 Auditory ossicles, in toto 



225 Inner ear (internal ear or labyrinth) 



226 Cochlea 



227 Semicircular canals 



228 Posterior semicircular canal 



229 Superior semicircular canal 

 22A Lateral semicircular canal 

 22B Ampulla 



22C Utricle 



22D Saccule 



22E Cochlear duct 



139 Auditory nerve 



23 Organ of equilibrium (balancing organ). (Use one of the specific symbols, 23-, below. ) 

 231 Statocyst (Crustacea) 



227 Semicircular canals 



256 Proprioceptor sensory nerve end organs; kinesthetic nerve end organs 



24 Chemoreceptor organs. (Use one of the specific symbols, 24-, below. ) 



241 Gustatory receptor; tastebuds 



242 Olfactory receptors (nasal receptors of vertebrates; invertebrate receptors such as 



antennal olfactory receptors) 



25 Mechanoreceptors (specific touch receptors, temperature receptors, pain receptors, and 



proprioceptors) 



251 Specific touch receptor (Meissner's corpuscle) 



252 Specific cold receptor (Krause's end bulb) 



253 Specific heat receptor (Ruffini's end organ) 



254 Specific pressure receptor (Pacinian corpuscle) 



255 Pain receptor 



2 56 Proprioceptors, in toto 



26 Specific tactile organs (particularly of invertebrate animals) 



261 Specific tactile tentacles 



262 Antennae, antennule 



3 Cardiovascular system 



31 Heart; pulsating vessel (both vertebrate and invertebrate vascular circulatory pumps) 



311 Atrium, auricle 

 3 ID Right auricle 



3 IE Left auricle 



312 Ventricle 



3 IF Right ventricle 



3 IG Left ventricle 



31L Sinus venosus (more primitive vertebrates) 



313 System of tissues conducting impulses across the heart; Bundle of His 



31A Pace maker. (For a single specifically named pace maker, use Symbols 31B or 31C. Note 

 also the structures 32M and 32N which affect cardiac pace. ) 



314 Cardiac valve, including the cardiac ostial valves (pulmonary and aortic). (For a specific 



valve, use Symbols 3 IH, 311, 31J, or31K. ) 



31H Left auriculoventricular valve (mitral valve or bicuspid valve) 



311 Right auriculoventricular valve (tricuspid valve) 



31J Aortic valve (semilunar aortic valve) 



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