A Device for the Investigation of Head Injury Effected by Non-Deforming Head Accelerations 670905
The major contribution of this effort to the investigation of head injury is the design and construction of a machine having the following functional goals:
Delivery of a reproducible acceleration-time profile to a primate head.
Capability of increasing the acceleration magnitude while retaining a similar acceleration-time profile.
The path traversed by the head must be constrained during the acceleration.
The forces applied to the head must be distributed so as not to produce gross damage to the brain or skull.
The machine that has evolved is designated as the Head Acceleration Device II (HAD-II). Basically, this machine consists of an axial cam cut on the face of a flywheel, and the cam follower imparts the motion of the cam through a linkage to a helmet in which the test subject's head has been potted. The helmet is rigidly pivoted causing the head to be rotated through an arc of 45 degrees. The peak acceleration attained by the cam follower was 1250 g's, with a positive phase duration of approximately 3 milliseconds.
An initial sample of 26 anesthetized squirrel monkeys was run on HAD-II at acceleration levels that produced no effect on the test subject to levels that delivered fatal blows. Each animal experienced only one acceleration pulse and survivors were sacrificed five days post test, with the brain and spinal cord removed for pathological examination.
A probit analysis of the data was performed and results of this analysis compared with the earlier work of Ommaya, et al.