HISTORICAL REVIEW 
medulla of six cats. Shivering persisted in these animals after the 
lesion. It would be an attractive hypothesis to propose that the path- 
way described, which was found to be intact for shivering to occur, 
was the efferent pathway from the hypothalamus to the lower motor 
center for control of shivering. However, this hypothesis must be 
proposed with caution and final decision awaited for confirmatory 
evidence, preferably using unanesthetized animals. 
Electrical stimulation. A method currently used in electro- 
physiology for determining the site of control of a particular func- 
tion is to stimulate a point within the central nervous system and to 
observe the physiological response to stimulation. This technique 
has been usedeffectively in studies of respiration to determine loca- 
tion of the inspiratory and expiratory centers in the central nervous 
system. If stimulation of a point in the medulla oblongata invokes 
inspiration, then the point stimulated can be assumed to be located 
in the inspiratory center. This technique has been used by a number 
of observers in studying shivering. Akert and Kesselring (1951) in 
reviewing the extensive diencephalic stimulation data from the 
laboratory of Hess found a number of instances where stimulation 
of regions in and adjacent to the hypothalamus produced a tremor 
resembling shivering. The tremor was produced by low frequency 
stimulation of eleven points in eight cats. Six of these points were 
in the septum pellucidum, three were in the caudate nucleus, one in 
the thalamus, and one in the posterior hypothalamus. Birzis and 
Hemingway (1957) were able to produce a tremor similar to shiv- 
ering when nineteen points in the midbrain of four cats were stimu- 
lated. These points were on the pathway described previously which 
was established by lesion experiments; the region dorsolateral to 
the red nucleus and a region in the lateral pons where stimulation 
evoked shivering is shown in Figure 8. From the record below the 
figure, the onset of shivering after stimulation is shown. This is a 
continuous record of muscle electrical activity (electromyogram)in 
two muscle groups. After stimulation of apoint near the red nucleus, 
there was a brief latent period followed by shivering. With cessation 
of the stimulus shivering subsided during a brief after-discharge 
period of approximately five seconds. Interest in the septum pellu- 
cidum as a controlling center for shivering was again aroused by 
the work of Andersson (1957). He, like Akert and Kesselring, was 
able to induce shivering by stimulation of points in the septum 
pellucidum of goats. The role of the septum pellucidum in shivering 
21 
