James G. McCormick

Anesthetization of Porpoises for Major Surgery

Comparison of three porpoises (Tursiops truncatus and Lagenorhynchus obliquidens) given nitrous oxide with 18 given halothane, with complete documentation of reflexes and comprehensive physiological monitoring, showed halothane to be a suitable anesthetic for major surgery while nitrous oxide was found to be inadequate. In addition, sodium thiopental administered intravenously was successfully used to facilitate intubation procedures. This development eliminated the need to intubate awake porpoises.

Brain-spinal cord ratios in porpoises: Possible correlations with intelligence and ecology'

As a rough measure of intelligence, brain weight: cord weight ratios in small delphinids compared favorably with, but were slightly less than, this ratio in man. Not all delphinids studied were found to achieve the minimum 1000 gm brain weight correlate of language development in the human child. The average adult brain size in some small pelagic cetaceans was found to be about 800 gm, while the average for Tursiops truncatus, an estuarine species, was found to be about 1450 gm.

Cochlear Potentials of the Pigeon: Relationships to Age, Serum Cholesterol Level, and Atherosclerosis

The cochlear potentials of different breeds of pigeons were measured. Potentials of old pigeons that developed spontaneous carotid atherosclerotic plaques were generally 15–18 dB poorer in sensitivity than younger birds of the same breed with little or no evidence of plaques. In another breed of pigeon, resistant to spontaneous atherosclerosis, but susceptible to high‐cholesterol‐diet‐induced coronary atherosclerosis, differences in potentials were less clearly defined; however, both the older birds and younger diet treated birds tended to be less sensitive than young nondiet treated birds.

Function of the Porpoise Ear as Shown by Its Electrical Potentials

The function of the porpoise ear was studied with cochlear potential experiments on 15 anesthetized Tursiops truncatus and Lagenorhynchus obliquidens. By performing surgical manipulations during cochlear‐potential recordings, the following was found: (1) The external meatus of the porpoise is no more important for sound conduction to the ear than is the surrounding tissue of the head. (2) The ear drum and tympanic ligament are not necessary for the transmission of sound energy to the inner ear. A point‐source bone stimulation cochlear‐potential map of the body revealed that (1) the skull of the porpoise is acoustically isolated from the ear; and (2) the lower jaw bone is an effective transducer of sound energy to the ear when made to vibrate with displacement towards the approximate axis of the stapes. Underwater cochlear‐potential audiograms demonstrated good sensitivity for the porpoise at least as high as 100 kHz.

Anatomical, electrophysiological, and histological studies of dolphin auditory system: Establishment of a theory of hearing for dolphins.

Wever and I at Princeton University wanted to study hearing in dolphins utilizing Wever’s cochlear‐potential recording method, which directly reflects the performance of the ear’s mechanical system. A method of humane anesthesia for dolphins for electrophysiological studies did not exist. Preliminary studies by Ridgway with halothane anesthesia published in 1965 seemed promising and motivated me and Wever to collaborate with Ridgway. Subsequently, Ridgway and I tested and perfected the use of halothane anesthesia for dolphins. This led to a coast to coast collaboration on dolphin hearing between Ridgway at Naval Missile Center Point Mugu and me and Wever at Princeton. Ridgway shared his expertise in Marine Mammal Medicine not only with us, but with the world, and in the process he became an expert marine mammal neuroscientist. Our three way collaboration demonstrated that the dolphin hears by bone conduction, with the middle ear ossicles acting as an inertial mass relative to the sound received in the low...

AC cochlear potentials in an animal model for human atherosclerosis: Relationships to blood pressure, vascular disease, and blood coagulation

We have discovered an animal model, the white carneau pigeon, which for the first time, through its use in laboratory experiments, has demonstrated significant correlations between the magnitude of inner ear electric potentials and standard measures of blood pressure, blood cholesterol, and blood coagulation. Also, we have found that a new blood coagulation research tool—the sonoclot machine—can demonstrate blood coagulation physiology parameters which correlate highly with cochlear potentials in our animal model. The above results will be discussed in relation to our previous findings of relationships of atherosclerosis to hearing in the same animal model. [Work supported by NIH Grant Number NS‐12013.]

Cochlear potentials of the pigeon: relationships to age, serum cholesterol level, atherosclerosis, and blood coagulation factors

Previously we reported [J. G. McCormick, R. M. Clayton, and I. L. Holleman, J. Acoust. Soc. Am. 52, 193 (1972)] that round window cochlear potentials of old pigeons that developed spontaneous carotid atherosclerotic plaques were poorer in sensitivity than younger birds of the same breed with little or no evidence of plaques. We also noted that a high cholesterol diet fed to these birds was correlated with a reduction of cochlear potentials. This initial work, which included studies on birds genetically resistant to atherosclerosis was a pilot project on 75 birds. In our present paper we will report further findings from a one year study of over 220 additional atheroselerotic pigeons. The age relationship to cochlear potential loss is substantiated, and correlative sophisticated blood coagulation tests will be discussed. [Work supported by NIH Grant No. NS‐12013 and Bowman Gray School of Medicine, Venture Capital Grant No. 2‐156‐801‐2507.]

Cochlear Dysfunction Associated with Decompression from 300‐ft Hyperbaric Chamber Dives

J. D. Harris has reported [U. S. Naval Submarine Medical Center, Conn., Rep. No. 591 (5 Aug. 1969)] severe neurosensory hearing loss in Navy divers due to decompression sickness. In an attempt to develop an animal model for this condition with verification of cochlear involvement, we compressed guinea pigs at 1 atm/min to 300 ft in air. Time at 300 ft was held constant at 6 min while decompression schedules were shortened from Navy diving tables. Animals were dived with an open bulla to eliminate barotrauma to the ear drum, and cochlear potentials were measured postdive. The general finding was the onset of auditory loss 10–15 min postdive. Severe loss (40–50 dB} was usually present by at least 1 h postdive. The loss remained stable 2–5 h postdive, and became more severe 6 h postdive.

Auditory and Vestibular Effects of Helium‐Oxygen Hyperbaric Chamber Dives to Convulsion Depths

Compressing at 24 atm/h, guinea pigs were dived in a helium‐oxygen environment (0.5 atm oxygen) to a depth where the animals convulsed—2640 ft (80 atm) to 2970 ft (90 atm). A modified Haldane decompression profile was used (28 h, 11 min from 80 atm, 22 h, 18 min from 90 atm). Post‐dive auditory function was assessed with cochlear potential measurements. Animals with myringotomies and tubes did not convulse significantly deeper than nontubed animals. One animal exhibited post‐dive bends symptoms. This animal also had severe post‐dive vestibular disorders and a severe neurosensory hearing loss. All other animals had severe or slight loss of auditory function. Much of this loss was conductive due to ear drum barotrauma. Some loss was probably neurosensory due to barotrauma or some yet undefined cause. The vestibular loss noted was similar to vestibular loss previously observed in four squirrel monkeys after two hydrogenoxygen dives.

Sensitivity of the Green Sea Turtle's Ear as Shown by Its Electrical Potentials

Both aerial and bone‐conduction cochlear‐potential runs demonstrated similar frequency sensitivity curves. Maximum sensitivity was in the 400‐Hz region, dropping off rapidly above and below. A point‐source bone‐stimulation cochlear‐potential study of the Green Sea Turtles head showed that the most sensitive receiving area is over the head of the columella.