Abstract
Chronic, progressive, bilateral exophthalmos has been produced in more than 150 prepubertal rabbits maintained on a diet of alfalfa hay and oats by the daily intramuscular injection of 0.05-0.1 cc. of methyl cyanide. 1 , 2 Feeding fresh vegetables markedly inhibits its development. Exophthalmos may appear as early as the 14th day and as late as the 60th day after beginning the cyanide injections. Males are much more susceptible and some breeds (Dutch) are more susceptible than others (Belgian). The degree of exophthalmos obtained has been highly variable in rabbits of the same age, sex and breed, but it is always proportional to the degree of thyroid hyperplasia (goiter) present.
We believe it is established that the initial cause of the exophthalmos is dependent primarily upon an increased tonicity and spastic contraction of the smooth muscles of the orbit and eyelids which are brought about by stimulation through the autonomic nervous system.
1. Dividing the cervical sympathetic trunk in 3 rabbits below the superior cervical ganglion definitely diminished the exophthalmos on the operated side when the animals were quiet, and particularly reduced the spasm of the lower eyelid. If the animal was disturbed, however, the exophthalmos became as marked as on the intact side.
2. Removal of the superior cervical ganglion permanently abolished the exophthalmos on that side in 6 animals.
3. Curetting the medulla of both suprarenals was without effect on existing exophthalmos in 3 animals, nor did it hasten or delay the onset of exophthalmos. Curetting the right suprarenal medulla and removing the left suprarenal gland in 18 rabbits was also without definite effect.
4. Thyroidectomy in 13 prepubertal rabbits hastened the onset of exophthalmos and increased it when performed after exophthalmos had developed.
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