HISTORICAL REVIEW 
Apparatus Used for Testing Cold Responses of Animals 
In studying the responses of homeothermic animals to cold, the 
animals used for testing have been mainly men, dogs, cats, and rats. 
The advantages and limitations of using men are well known. Of the 
various animals available for stucfy, there are certain anatomical 
and physiological characteristics of dogs, cats, and rats which make 
them useful for special purposes. Dogs and cats have a well-dev- 
eloped shivering mechanism which is similar in all respects to that 
of man. The presently well-known control for starting, stopping, and 
regulating shivering in these animals is identical with that of man. 
This is not true for the physiological response to heat. Where 
metabolic, circulatory, and respiratory investigations are being 
made and where adequate samples of blood for analysis are needed, 
the dog is the animal of choice. In addition, the dog can be trained 
to lie motionless on a table or platform without restraint. This is 
a most important characteristic where studies are made of mild 
shivering, or in attempts to separate the metabolism of shivering 
from nonshivering thermogenesis. The cat is particularly valuable 
where studies of the nervous system are required. The neuroana- 
tomy and neurophysiology of the cat are probably as well, if not 
better, understood than that of man. This is a result of the popular 
usage of the cat for studies of the nervous system because of the 
uniformity of the shape of the head of the cat for stereotaxis studies, 
and the ease, convenience, and cost of the cat in handling and main- 
tenance. For such considerations, the monkey, although useful, 
is much less popular. The rat, due to its omnivorous diet, is use- 
ful for nutritional studies. It shivers well in the cold and is a 
fairly good homeotherm. Apparently, however, the rat differs in its 
response to cold from the larger animals, relying on nonshivering 
thermogenesis. 
The apparatus which has been found the most useful for stucfying 
shivering in the dog (Hemingway and Hathaway, 1941) is shown in 
Figure 1. The trained dog lies on his side in a double-walled box 
with either cold or hot water being circulated through the space 
between the walls. A glass window inthe cover permits observation 
of the animal. The shoulders and chest of the dog are supported 
by a fixed platform, while the hind legs rest on a platform suspended 
