Tracheostomies were performed on 25 mongrel dogs, employing either a vertical or inverted U flap incision in the trachea. Following cannulation for 14 days, the animals were maintained for three months and endolarygeal photographs were taken. At the time of autopsy, comparisons of the gross specimens were carried out, as well as histological sectioning through the tracheal stomal area. Both endolaryngeal examination and study of the gross specimens at autopsy revealed less distortion of the tracheal lumen following the flap versus vertical tracheostomy, especially in those animals having the flap of cartilage resewn to the trachea at the time of decannulation. Measurements of the cross sectional area at the tracheal stoma were also made. In animals having a flap tracheostomy, the stomal lumen was preserved, regardless of resuturing the flap. However, animals having a vertical tracheostomy lost an average of 18% of the tracheal area when compared with those having a flap incision. Histological examination revealed cartilaginous growth across the tracheostomy incision only in animals having the flap tracheostomy. Support for the flap tracheostomy is provided from animal experimentation.

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Miller and Davis (1963) have reported that rats receiving brief electric shocks pressed a bar that led to an injection of amobarbital more frequently than yoked control rats who were injected when their experimental partners pressed the bar but whose own bar activated only a counter. This reinforcing effect of amobarbital, however, was short-lived. Experimental rats increased their bar pressing rate in comparison with the yoked controls during three daily one hour test periods, but on the following three days their rates declined reaching the same level as the control animals.Amobarbital seems to have a significant but temporary reinforcing

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